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THE
VOYAGE OF H.M.S. CHALLENGER.
ZOOLOGY--VOL. XVIII.
SECOND PART.
REPORT
ON THE
SCIENTIFIC RESULTS
OF THE
VOYAGE OF H.M.S. CHALLENGER
DURING THE YEARS i873-76
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t
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ZOOLOGY— VOL. XVIII.
SECOND PART
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1887
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CONTENTS.
EEPORT on the RADIOLARIA collected by H.M.S. CHALLENGER during the years
1873-1876.
By ERNST HAECKEL, M.D., Ph.D., Professor of Zoology in the University of Jena.
SECOND PART.— OSCULOSA. (NASSELLARIA AND PH^EODARIA.)
CONTENTS.
SECOND PART.
PAGE
II. Subclass OSCULOSA, ... 889
Legion III. NASSELLARIA vel MONOPYLEA, . 889
Order 11. NASSOIDEA, .... 895
„ 12. PLECTOIDEA, . . . 898 ,, 13. STEPHOIDEA, .
„ 14. SPYROIDEA, .... . 1015 „ 15. BOTRYODEA, .
„ 16. CYRTOIDEA, ... 1126
Legion IV. PH^ODARIA vel CANNOPYLEA, . 1521
Order 17. PH.EOCYSTINA,
' „ 18. PH^EOSPH^ERIA, . . 1590
„ 19. PHJEOGROMIA, . !642
„ 20. PH.EOCONCHIA, . ^710
NOTE ON THE DIMENSIONS AND MEASUREMENTS, . . 1760
ADDENDA, . 1761
EKRATA, . !763 INDEX, .
REPORT ON THE RADIOLARIA. 889
Legion III. NASSELLARIA, vel Monopylea, vel Monopylaria (Pis. 51-98).
Nassellaria (inclusis Spyridinis), Ehrenberg, 1875,
Monopylea, Hertwig, 1879.
Monopylaria, Haeckel, 1881.
Oyrtida et Acanthodesmida, Haeckel, 1862,
Definition. — Kadiolaria with simple membrane of the central capsule, which is monaxon or bilateral, and bears on one pole of the main axis a porous area (porochora), forming the base of a peculiar intracapsular cone (podoconus). Extra- capsulum without phseodium. Skeleton siliceous, very rarely wanting. Fundamental form originally monaxon, often dipleuric or bilateral.
The legion NASSELLARIA vel MONOPYLEA, in the extent here denned, was constituted in 1879 by Richard Hertwig in his work Der Organismus der Eadiolarien (pp. 133-137). He gave to this large group the rank of an order, and united in it the two families Acanthodesmida and Cyrtida, which I had constituted first in 1862 in my Monograph (pp. 237, 265, 272); but he added, too, as a third family the Plagiacanthida, united by me with the former. In the first system of Ehrenberg (1847, loc. cit., pp. 53, 54), four families belonging to the MONOPYLEA were enumerated, the Halicalyptrina, Lithochytrina, Eucyrtidina, and Spyridiiia. He united the three former under the name." Polycystina solitaria," which he afterwards changed into NASSELLARIA (1875, Abhandl. d. k. Akad. d. Wiss. Berlin, p. 157).
In my Monograph of the Radiolaria (1862, pp. 265—345) forty -four genera of NASSELLARIA were enumerated (six Acanthodesmida and thirty-eight Cyrtida), whilst the total number of genera in the whole class of Radiolaria at that time amounted to one hundred and thirteen. But owing to the astonishing number of new and interesting forms of this legion which I afterwards detected in the collection of the Challenger, in 1881 I distinguished in my Prodromus not less than three hundred and seventeen genera. These were disposed in five large main groups, retained in the present Report, with twenty -six families, viz., (1) Plectoidea (with three families), (2) Ste- p h o i d e a (with four families), (3) Spyroidea (with four families), (4) Botryodea (with three families), and (5) Cyrtoidea (with twelve families). The first two groups have an incomplete or rudimentary skeleton, and may be united in the order Plectellaria, whilst the other three families possess a complete latticed shell, and
(ZOOL. CHALL. EXP. — PART XL. 1885.) Rf 112 ^
890 THE VOYAGE OF H.M.S. CHALLENGER.
may be united as Cyrtellaria. The former correspond to the Acanthodesmida, the latter to the Cyrtida in my Monograph.
The character common to all MONOPYLEA or NASSELLARIA, which separates them from all other Eadiolaria, was first recognised by Eichard Hertwig in 1879, and consists in the singular structure of the monaxonian central capsule, bearing on the basal pole a peculiar porous area or operculum, the " Porenfeld;" we call it shortly the " porochora." It represents a circular or elliptical porous plate on the basal pole of the vertical main axis of the central capsule, and bears a peculiar " podoconus " or " Pseudopodien-Kegel," a conical body of singular structure, protruding inside the membrane into the capsule. The pseudopodia arising from this peculiar " podoconus " proceed from the capsule piercing the " porochora," whilst the other parts of the capsule are not perforated.
The MONOPYLEA are therefore " Merotrypasta," like the following fourth legion, the PH^EODARIA or CANNOPYLEA. But in these latter we find on the basal pole of the monaxonian capsule only one single large main opening, prolonged into a peculiar tube, and there is no trace of the typical " podoconus," characteristic of all NASSELLARIA. The latter agree, however, with the former in the possession of a basal opening, serving for the emission of the pseudopodia, and in the monaxonian fundamental form, arising from this structure. Therefore these two legions of " Merotrypasta " exhibit a wider divergence from the ACANTHARIA and SPUMELLARIA, the two legions of " Holotrypasta," in which the central capsule is everywhere perforated by innumerable small pores (com- pare above, pp. 5, 6, 716).
The Skeleton in all NASSELLARIA consists either of pure silica, or of a peculiar silicate ; never of acanthin (as in all ACANTHARIA). The siliceous bars and beams constituting it are invariably solid (as also in the SPUMELLARIA) ; never hollow (as in the PH^ODARIA). In the small family of Nassellida alone (with the two genera Cystidium and Nassella) the skeleton is entirely absent. In all other genera of NASSELLARIA the siliceous skeleton is more or less developed ; imperfect, or quite rudimentary in the Plectellaria (Plectoidea and Stephoidea), but perfect and forming a regular lattice-shell in the Cyrtellaria (Spyroidea, Botryodea, and C y r t o i d e a). The different forms of this skeleton exhibit an extraordinary variety, but may be reduced to a few very simple fundamental forms, or even to a single, most simple original form. The comparative morphology is more interesting, but also more difficult to understand than in any other Eadiolaria.
The geometrical fundamental form of the skeleton is in all NASSELLARIA monaxonial, the vertical main axis of the body, which is already indicated by the axis of the central capsule with two different poles, being also expressed constantly in the form of the skeleton. The lower or basal pole of the latter always exhibits a different shape from that of the upper or apical pole. This difference is so striking in nearly all MONOPYLEA, that the two poles may be determined on the first view.
REPORT ON THE RADIOLARIA. 891
In the great majority of NASSELLARIA not only is the monaxonial fundamental form expressed, but also the dipleuric or bilateral, so that the symmetrical halves of the body may be easily determined ; the right and left halves exhibit the same symmetry as in the vertebrates, so that we may distinguish an anterior ventral and a posterior dorsal face of the body. The whole form is in this case determined by three dimensive axes, perpendicular to one another, two of which are heteropolar, the third is homceopolar. The apical pole of the vertical main axis (principal or longitudinal axis) is different from the basal pole. The ventral pole of the horizontal sagittal axis (or dorso-ventral axis) is different from the dorsal pole. The right pole of the horizontal transverse axis (lateral or frontal axis) is equal to the left pole. Therefore the sagittal or median plane of the body (in which the principal and the sagittal axis are crossed) divides it into symmetrical equal halves and is perpendicular to the frontal axis.
Three different original elements of structure are recognisable in the majority of NASSELLARIA, viz., (l) a vertical simple ring, the primary or sagittal ring, placed vertically in the sagittal plane and enclosing the median plane of the central capsule ;
(2) a basal tripod, composed of three diverging radial rods, which are united on the basal pole of the central capsule and are either expanded horizontally or descend ;
(3) an ovate or subspherical, simple lattice-shell, the cephalis or capitulum, which sur- rounds the central capsule and exhibits a peculiar structure on its basal pole.
These three important original elements of structure — the sagittal ring, the basal tripod, and the latticed cephalis — are so united in the majority of NASSELLARIA that the cephalis rests upon the tripod and includes the sagittal ring wholly or partially. The simplest realisation of this typical union is afforded by the Archiperida and Tripospyrida, and these may be derived from the simpler important Stephanid Cortina (PL 83, fig. 9 ; PI. 92, fig. 21 ; PL 97, fig. 1). In this and in all other tripodal NASSELLAEIA, the three basal rods or the " cortinar feet " are constantly so arranged that an odd or posterior rod, the " caudal foot " (c) is opposed to the two anterior paired rods, the " pectoral feet " (one right, p", and one left, p']. The caudal foot lies in the sagittal plane, and is prolonged upwards into the dorsal rod of the sagittal ring (V), and over this in a free ascending spine, the " apical horn " (a). The curved ventral rod of the ring (r) is united above with the base of the apical horn, below with the common centre of the tripod or the " cortinar centrum." The characteristic position of the central capsule in this skeleton of Cortina is such that its basal pole (with the porochora) rests upon the centre of the tripod, whilst its sagittal perimeter is separated from the surrounding ring by the calymma ; the numerous pseudopodia arising from its base diverge downwards and are supported and protected by the three basal feet of the tripod (PL 97, fig. 1). Compare also Pis. 51, 53, 84, 95, 98.
The typical skeleton of Cortina, a tripodal ring, becomes more developed in the Semantid Cortinisciis, in which the basal parts of the three diverging feet are united
892 THE VOYAGE OF H.M.S. CHALLENGER.
by a second horizontal ring, the cortinar or basal ring (PI. 92, figs. 11-13). The pores between the former and the latter, or the " cortinar pores," may be regarded as the first beginning of the lattice -plate, composing the " cephalis " or the simple primordial shell in the Archiperida and Tripospyrida, and transmitted from these by heredity to the great majority of NASSELLARIA.
The "cephalis or capitulum " (the "Kopfchen" of the German authors) is therefore the most important part of the skeleton in all C y r t e 1 1 a r i a, or in all NASSELLARIA possessing a complete lattice-shell. In the Plectellaria, however, or in those NASSELLARIA which do not possess a complete fenestrated shell, the " cephalis " is either imperfect or totally wanting. The cephalis surrounds the enclosed central capsule on all sides in the form of an ovate or subspherical lattice -shell, and is separated from it only by the jelly-like calymma. The sagittal ring is either enclosed in the wall of the cephalis (wholly or partially), separating its two lateral halves, or it is enclosed in the cavity of the cephalis and connected with its sagittal perimeter by short beams. The base of the cephalis (with the cortinar plate) often rests immediately upon the centre of the tripod ; in the majority of NASSELLAEIA, however, this near relation is altered by reason of later changes and secondary modifications.
The number of various forms, developed from these simple original structural elements of the skeleton, is astonishing, and there are described more than three hundred genera and nearly two thousand species of this legion in the following pages. This large number may be easily increased by subsequent observers. Since in all these MONOPYLEA the characteristic structure of the central capsule is identical, and also the structural elements of the siliceous skeleton are similar, it is very probable that they may have arisen from a single common stock. But it is very difficult (and at present impossible) to explain a natural monophyletic system of this large legion. The greatest difficulty is presented by the fact that the three structural elements mentioned above, viz., the sagittal ring, the basal tripod, and the latticed cephalis, are not constantly united, but each alone may also constitute the skeleton by itself. In this respect the following seven cases are possible, and are actually realised.
A. The skeleton is composed of the sagittal ring only and of its spiny appendages, without basal tripod and without latticed cephalis. This is the case in the majority of Stephoidea (Stephanida, Semantida, Coronida, and Tympanida).
B.. The skeleton is composed of a basal tripod only (Plagiacantha), or of a tripod in the centre of which arises a vertical apical horn (Plagoniscus), and often of an irregular framework, arising from the rods of the tripod ; but there is neither a trace of a sagittal ring nor a complete latticed cephalis. This is the case in the remarkable suborder Plectoidea (Plagonida and Plectanida).
C. The skeleton is composed of a latticed cephalis only, a simple ovate or sub- spherical fenestrated shell, which encloses the monopylean central capsule; there is no
REPORT ON THE RADIOLARIA. 893
trace of a sagittal ring nor of a basal tripod. This is the case in the remarkable family of Cyrtocalpida (Archicorida and Archicapsida), in numerous Botryodea and in other Cyrtellaria.
D. The skeleton is composed of a sagittal ring and a basal tripod, without latticed cephalis. This is the case in a few, but very important forms of Stephoidea: Cortina, Stephanium, Cortiniscus, Stephaniscus, Podocoronis, and some allied genera.
E. The skeleton is composed of a sagittal ring and a latticed cephalis, but without basal tripod. This is the case in numerous Cyrtellaria, in the Circospyrida (or Zygospyrida apoda: Dictyospyris, Circospyris) and some other Spyroidea; and in a large number of Botryodea and Cyrtoidea eradiata (a part of the Sethocyrtida, Theocyrtida, Lithocampida, and others).
F. The shell is composed of a basal tripod and a latticed cephalis, but without any trace of the sagittal ring. This is the case in numerous Cyrtoidea triradiata and multiradiata, and perhaps in the majority of the following families — Tripocalpida, Tripocyrtida, Podocyrtida, and Podocampida.
G. The shell is composed of all three above-mentioned elements, of a sagittal ring, a basal tripod, and a latticed cephalis. This is the case in the great majority of Spyroidea (with a few exceptions only), and perhaps also in the majority of Cyrtoidea.
The survey of these seven groups, A to G, each of which is represented by numerous living forms, shows clearly how difficult and complicated the morphology and phylogeny of the numerous NASSELLARIA must be. For all possible combinations of the three original structural elements are realised abundantly, and in such compli- cated relations, and so intermingled in the different orders and families, that it seems nearly hopeless to answer the question of their true origin. The identity in the structure of the central capsule, however, in all these MONOPYLEA, makes it probable that they have all arisen originally from the skeletonless Nassellida (Cystidium, Nassella), either in a monophyletic or in a polyphyletic way. In this respect the following phylogenetical hypotheses are possible.
1. Monophyletic hypothesis, deriving all NASSELLARIA from a simple sagittal ring (Archicircus, Lithocircus, &c., PI. 81). The groups A, D, E, and G may be derived easily from such a ring, but the groups B, C, and F only by means of the hypothesis that the original ring may be completely reduced and finally lost. This hypothesis was stated by me in the years 1877 to 1879, when I had got the first general survey of the astonishing number of new NASSELLARIA in the Challenger collection, and as I had found the sagittal ring in the majority of them. This, my former hypothesis, is mentioned by Eichard Hertwig (1879, loc. cit., pp. 68, 126). It was afterwards supported with particular energy by 0. Biitschli (1882, Zeitschr. fur wiss. Zool., Bd. XXXVI. ).
2. Monophyletic hypothesis, deriving all NASSELLARIA from a basal tripod (Triplagia, Plagoniscus, &c., PI. 91). The groups B, D, F, and G, all triradiate, may
894 THE VOYAGE OF H.M.S. CHALLENGER.
be derived easily from such a tripod ; but the groups A, C, and E only by means of the hypothesis that the original tripod may be completely reduced and finally lost. This hypothesis was employed in 1881 in my Prodromus, since I had convinced myself that the " triradial structure " is prevalent in the great majority of NASSELLARIA, and is perhaps more important than the sagittal ring.
3. Monophyletic hypothesis, deriving all NASSELLARIA from a latticed cephalis, a simple ovate or subspherical fenestrated shell without ring and tripod (Cyrtocalpis, Archicapsa, &c.). The groups C, E, F, and G may be derived easily from such a cephalis, but the groups A, B, and D only by means of the hypothesis that the sagittal ring as well as the basal tripod may remain as the last remnants of a reduced cephalis. This hypothesis was given in 1862 in my Monograph, where I constructed the first pedigree of Eadiolaria (p. 234). I there derived all the Cyrtida from the Sphseroidea (Cyrtidosphcera), supposing that Cyrtocalpis and some other Monocyrtida may form a direct phylogenetical passage from the Sphseroidea to the Cyrtoidea.
4. Polyphyletic hypotheses, deriving the different groups of NASSELLARIA from different skeletonless Nassellida, by development of simple siliceous skeletons in different ways. Among the numerous polyphyletic hypotheses which are possible, one of the simplest would be the supposition that three different fundamental forms of skeleton may have arisen independently one from another : (l) a simple sagittal ring as original form of the Stephoidea and Spyroidea (A) ; (2) a simple basal tripod as original form of the Plectoidea (B) ; (3) a simple latticed cephalis as original form of the Botryodea and Cyrtoidea (C). This triphyletic hypothesis is supported by R. Hertwig (1879, loc. cit., p. 136); he assumes that the original skeletonless Nassellida (Cystidium) have produced three different branches, his " Acanthodesmida " (=Stephoidea and Spyroidea) with a primary ring, his " Plagiacanthida " ( = Plectoidea) with a primary tripod, and his Cyrtida (=Botryodea and Cyrtoidea) with a primary cephalis. This hypothesis seems rather probable on the first view ; but it meets with the greatest difficulties in view of the fact that these three original elements of the skeleton are more or less evidently combined in the great' majority of NASSELLARIA. The greatest difficulty arises from the fact that often among very similar and closely allied forms the first exhibits all three elements (A, B, C) com- bined, whilst the second has a combination of A and B, the third of B and C, the fourth of A and C ; and there are other forms, very similar to the former, in which one element only is recognisable. Another difficulty arises from the fact that the intimate structure of the cephalis in the majority ofCyrtellariais not perfectly known, and often exhibits structures which are difficult to explain with regard to the three elements A, B, C. Under these circumstances further researches on the numerous imperfectly known NASSELLARIA are required, and chiefly accurate observations on their more minute structure and on their important ontogeny.
REPORT ON THE RADIOLARIA.
895
We divide the immense legion of NASSELLARIA into two large orders, the Plectellaria without complete lattice-shell, and the Cyrtellaria with a complete lattice-shell or a "cephalis," including the central capsule; the latter, of course, have arisen from the former. The Plectellaria comprise three different suborders, the Nassoidea (without skeleton), the Plectoidea (with a tripodal skeleton, without ring), and the Stephoidea (with a primary sagittal ring, with or without tripod). The Cyrtellaria again also comprise three different suborders, the Spyroidea (with bilocular cephalis and a sagittal constriction), the Botryodea (with multilocular and lobate cephalis, exhibiting two or more constrictions and three or more lobes), and the Cyrtoidea (with simple, unilocular cephalis, without con- striction).
Synopsis of the Orders and Suborders of NASSELLAKIA.
No skeleton, . . . .1. Nassoidea.
I. Order
PLECTELLARIA.
Nassellaria without complete lattice-shell.
II. Order
CYRTELLARIA. Nassellaria with a complete lattice-shell.
Skeleton with a basal tripod, without
ring, . . . . .2. Plectoidea.
Skeleton with a sagittal ring (usually
without tripod), . . . 3. Stephoidea.
Cephalis bilocular, with a sagittal con- striction, . . . .4. Spyroidea.
Cephalis multilocular, with two or more
constrictions and lobes, . . 5. Botryodea.
Cephalis simple, without constriction and lobes, . . . . .6. Cyrtoidea.
Order V. PLECTELLARIA, Haeckel, 1883.
Definition, — NASSELLARIA without complete lattice-shell, usually with an incomplete skeleton, formed of a ring, a tripod, or an irregular framework
Suborder I. NASSOIDEA, Haeckel. Definition. — NASSELLARIA without skeleton. Single family Nassellida.
896 THE VOYAGE OF H.M.S. CHALLENGER.
Family XLV. NASSELLIDA, Haeckel.
Cystidina, Haeckel, 1883, Sitzungsb. Jena Ges. fur Naturw., Februar 16.
Definition. — NASSELLARIA without skeleton. The soft body composed of a monopylean central capsule (with porochora and podoconus) and of a surrounding jelly- veil or calymma.
The family Nassellida comprises the simplest and most primitive forms of NASSELLARIA, the only group which is entirely without a skeleton. The central capsule is therefore perfectly free and naked, enveloped by the calymma only, as in the Colloidea among the SPUMELLARIA, in the Phseodinida among the PH^EODARIA. Probably these naked and skeletonless MONOPYLEA must be regarded as surviving remnants of the common ancestral group of this legion ; but the possibility is not excluded that the few observed forms are either young NASSELLARIA which have not yet secreted a skeleton, or older NASSELLARIA which have lost their original skeleton.
We distinguish in this small family two genera only : Cystidium with hyaline, not foamy calymma, without extracapsular alveoles, and Nassella, with a very voluminous foamy calymma, including numerous large alveoles ; the former corresponds to Actissa and the latter to Thalassicolla among the Colloidea or the skeletonless SPUMELLARIA. But in these two latter genera, as in all PERIPYLEA, the central capsule is perforated everywhere by innumerable small pores ; the two former genera, however, exhibit the same characteristic podoconus in the central capsule, and the same porochora at its base, as all the other MONOPYLEA. The pseudopodia are protruded from the central capsule through the porochora only.
TJie Central Capsule is in the two observed genera either ovate or nearly spherical, usually slightly tapering towards the basal mouth. Its transverse section is constantly circular. The membrane of the capsule is usually rather thick and double-contoured, and bears on the truncate basal pole a circular " porochora " or area porosa, through which the pseudopodia are protruded. The porochora is either quite simple, circular, or in some species trilobed, with three equal circular lobes, each of which is surrounded by a girdle of small granules. The £>odoconus, or " pseudopodial-cone," arising vertically from the horizontal basal porochora, is half as long as the central capsule, or longer, simply conical and finely striped longitudinally. The nucleus lies usually in the upper- most part of the central capsule, above or behind the podoconus, and is either spherical or ovate, sometimes kidney-shaped. It includes one or more nucleoli.
Synopsis of the Genera of Nassellida.
Calymma hyaline, without alveoles, ....... 382. Cystidium.
Calymma foamy, with numerous large alveoles, ..... 383. Nassella.
REPORT ON THE EADIOLARIA. 897
Genus 382. Cystidium,1 E. Hertwig, 1879, Organismus d. Eadiol., p. 87. Definition. — N assellida with hyaline calymma, without extracapsular alveoles.
The genus Cystidium is the simplest and most primitive among all NASSELLARIA, and may be regarded as the common ancestral form of this legion, for which it has the same high importance as Actissa for the SPUMELLARIA. The central capsule is quite simple, ovate or nearly spherical, and included in a voluminous hyaline calymma, which contains no large alveoles. Cystidium differs from Actissa, its probable ancestral form, in the possession of the " podoconus " and its basal " porochora," characteristic of all NASSELLARIA or MONOPYLEA.
1. Cystidium princeps, n. sp. (PL 91, fig. 1).
Central capsule ovate, one and a third times as long as broad. Podoconus with simple circular porochora, about half as long as the capsule, surrounded at its base by red granules of pigment. Nucleus spherical. Three equal oil-globules in the endoplasm. No pigment in the voluminous calymma, which includes numerous xanthellae.
Dimensions. — Length of the central capsule 01, breadth 0'075 ; nucleus 0'035.
Habitat. — Indian Ocean, Maldive Islands (Haeckel), surface.
2. Cystidium lecythium, n. sp.
Central capsule ovate, one and a half times as long as broad. Podoconus with simple circular porochora, three-fourths as long as the capsule. Nucleus ellipsoidal. No oil-globules in the endoplasm. No pigment and no xanthellae in the calymma.
Dimensions. — Length of the central capsule 0'12, breadth O08 ; nucleus 0'04
Habitat. — Central Pacific, Station 271, surface.
3. Cystidium inerme, E. Hertwig.
Cystidium inerme, R Hertwig, 1879, Organismus d. Radio!., p. 87, Taf. vii. figs. 1-16.
Central capsule subspherical, a little longer than broad. Podoconus about two-thirds as long as the capsule, with trifid porochora, which is composed of three equal circular lobes. Nucleus spherical. Numerous oil-globules in the endoplasm. The calymma includes numerous xanthellse and brown pigment around the mouth.
Dimensions. — Length of the central capsule 0'06, breadth 0'05 ; nucleus 0'03.
Habitat. — Mediterranean, Messina (R Hertwig), surface.
1 Cystidium= Small vesicle ; xvirrKiov.
(ZOOL. CHALL. EXP. — PART XL. — 1885.) Rr 113
898 THE VOYAGE OF H.M.S. CHALLENGER.
Genus 383. Nassella,1 nov. gen.
Definition. — N assellida with foamy calymma, containing numerous large extracapsular alveoles.
The genus Nassella differs from the preceding Cystidium, its probable ancestral form, in the development of numerous large alveoles in the extracapsular calymma, and therefore exhibits the same relation to it that Thalassicolla bears to Actissa among the SPUMELLARIA. The foamy calymma is very voluminous, and includes numerous symbiotic xanthellae.
1. Nassella thalassicolla, n. sp.
Central capsule spherical. Podoconus with simple circular porochora, half as long as the capsule. Nucleus spherical. Numerous oil-globules in the endoplasm. Calymma spherical, without pigment, with numerous xanthellse and large alveoles.
Dimensions. — Diameter of the central capsule 012, nucleus 0'04, calymma 0-6.
Habitat. — South Pacific, Station 300 (off Juan Fernandez), surface.
2. Nassella nassiterna, n. sp.
Central capsule ovate. Podoconus two-thirds as long as the capsule, trifid, with three equal circular lobes (as in Cystidium inerme). Nucleus ovate. Three equal large oil-globules in the endoplasm, corresponding to the three lobes of the porochora. Calymma ovate, in the upper half much more voluminous than in the lower, including numerous large alveoli and xanthellse, and around the mouth masses of black pigment.
Dimensions. — Diameter of the central capsule O'l, nucleus 0'03, calymma 0'8.
Habitat. — Indian Ocean, Madagascar (Rabbe), surface.
Suborder II. PLECTOIDEA, Haeckel.
Plectoidea vel Plectida, Haeckel, 1881, Prodromus, p. 423.
Plagiacanthida (sensu ampliori), R. Hertwig, 1879, Organismus d. Radiol., p. 72.
Definition. — NASSELLARIA with a rudimentary, originally tripodal skeleton, composed of radial spines, arising from one common central point or central rod ; the spines are simple or branched, and the branches may form by concrescence of their meeting ends a loose wickerwork, but never a complete lattice-shell. Never a ring in the skeleton.
1 Nassella — Small wicker cage for fishing.
REPORT ON THE RADIOLARIA. 899
The suborder Plectoidea, hitherto known by few species only of "Plagiacanthida," comprises a large number of interesting NASSELLARIA, which belong partly to the simplest and most primitive forms of this legion. It may be divided into two different families, Plagonida and Plectanida. In the first family, Plagonida, the monopylean central capsule is supported by a simple or rudimentary skeleton, composed only of a variable number of radial spines united in a common centre. In the second family,' Plectanida, the branches of these radial spines become united and form a loose irregular framework with wide meshes, partly enclosing the central capsule, but never a perfect lattice-shell.
The Plectoidea differ from the following suborder, the Stephoidea, in the absence of the ring, characteristic of the latter. Some slight traces, however, indicate a near affinity between the ringless Plectoidea and the ring-bearing Stephoidea. Both these suborders of Plectellaria differ from the closely allied Cyrtellaria (Spyroidea, Botryodea, and Cyrtoidea) in the absence of a complete lattice-shell. The morphological relation and phylogenetic affinity between the former and the latter have already been discussed in the preceding description of the legion NASSELLARIA (compare pp. 891—894).
The first known species of Plectoidea was observed in the North Atlantic (on the Norwegian shore) in 1855 by my late friend Edouard Claparede, and described and figured in his Etudes, &.c. (1858), under the name Plagiacantha arachnoides. He considered it as a new genus of Acanthometrina. Another species, from the Mediterranean, was described in the same year by Johannes Muller as Acanthodesmia dumetum (1858, loc. cit., Taf. i. fig. 3). A third species, also Mediterranean, was figured by me in 1865 under the name Acanthodesmia polybrocha. Finally, Eichard Hertwig, 1879, in his Organismus der Eadiolarien, gave a very accurate description of another Mediterranean form, Plagiacantha abietina (loc. cit., Taf. vii. fig. 6). He first recognised the true character of MONOPYLEA in their monaxonian central capsule, and observed at the same time the first NASSELLARITTM without skeleton, called by him Cyrtidium inerme (loc. cit., Taf. vii. fig. 1). To these four known species, representing three different genera, the rich collection of the Challenger has added so many new forms that we may distinguish here not less than seventeen genera and sixty-one species. In my Prodromus (1881, p. 423) I arranged these in two subfamilies, the Plagonida and Plectanida, constituting together the family Plectida (identical with the " Plagiacanthida " of Hertwig and Blitschli). But at present, regarding the important relations of these Plectida to the other NASSELLARIA, it seems more con- venient to give to them the rank of an independent suborder of Radiolaria, under the name Plectoidea.
The peculiar structure of the central capsule of the Plectoidea, first recognised by Richard Hertwig, allows no doubt of their being true MONOPYLEA or NASSELLARIA ; and also their siliceous, originally triradiate skeleton indicates the nearest affinity to
900 THE VOYAGE OF H.M.S. CHALLENGER.
the other families of this legion. But a very difficult and as yet unsolved problem is the important question, in what manner these different groups of NASSELLARIA are phylogenetically connected. Either the Plectoide a — as the simplest of all — are the original common ancestral group of this whole legion (as I assumed in my Prodromus, 1881), or they are derived from the Stephoidea (by reduction of the sagittal ring), or they have originated independently from them (if we suppose a poly- phyletic origin of the MONOPYLEA. Compare above, p. 893, &c.). In any case the typical " triradial structure " of the Plectoide a, prevalent also in the other groups of this legion, is a very important and interesting fact.
The triradial skeleton of the Plectoidea exhibits in the two families of Plagonida and Plectanida a complete homology of development, so that each genus of the latter may be derived from a corresponding genus of the former, simply arisen by concrescence or union of the branches of the radial spines. Therefore the only difference between the two closely allied families is, that the branches of the radial spines in the Plagonida remain free, whilst in the Plectanida they produce a loose framework or wickerwork by union of their meeting ends. We express this complete homology in the nomenclature of the Plectoidea, in each genus of Plagonida retaining the syllable "Plag-" ; in each genus of Plectanida, correspondingly, the syllable "Plect-."
The number of radial spines composing the skeleton is originally three, and in all not triradial genera is probably derived from three. For better survey we may divide each family, according to the different number of rays, into four different subfamilies : A, with three radial spines (Triplagida and Triplectida) ; B, with four radial spines (Tetraplagida and Tetraplectida) ; C, with six radial spines (Hexaplagida and Hexaplectida) ; and D, with numerous (seven to nine or more) radial spines (Polyplagida and Polyplectida). The last three subfamilies have arisen probably from the first triradial subfamily, by a secondary increase in the number of rays.
The important signification of the triradial structure, recurring in the most different groups of NASSELLARIA, has been already pointed out sufficiently by myself and by R Hertwig. But the triradial Plectoidea offer also another interesting relation of this characteristic structure, some simple forms of this order appearing nearly identical with the isolated triradial spicula of certain Beloidea (Thalassosphserida and Sphserozoida). Even some more complex quadriradial and sexradial forms of the latter reappear in exactly the same shape also in the former. This identity may be perhaps an important indication of true affinity (compare below).
The simplest and probably the most original kind of triradial structure is exhibited by the genera Triplagia and Triplecta (PI. 91, figs. 2, 7). Here three equal radial spines lie in one horizontal plane and are united in a common central point at equal angles, so that three lines connecting their distal ends form a regular equilateral triangle. Simple triradial spicula of the same regular form are also found in many
REPORT ON THE RADIOLARIA. 901
Beloidea (Lainpoxanthium, Sphcerozoum, &c., Pis. 2 and 4). The central capsule of these simplest Plectoidea (with vertical main axis) rests perpendicularly on the horizontal triangle, formed by the triradial skeleton ; the porochora of the former (or the " area porosa ") rests upon the central point of the latter.
Another kind of triradial structure characterises the genera Plagiacaniha and Plectophora. The three radial spines united in the central point lie here not in one plane, but diverge in different planes, so that they correspond to the three lateral edges of a three-sided pyramid. Commonly the three spines are of equal size, and also the angles between them equal, so that the pyramid is regular, sometimes very flat, at other times more elevated. Spicula of exactly the same form are also found in some Beloidea. Probably the three divergent spines are homologous to the three basal feet of numerous Spyroidea and Cyrtoidea. The central capsule, accord- ing to Hertwig, is placed in the apical part of the pyramid, the axes of both being identical, and the porochora resting in the apex itself. This fact seems to contradict the above-mentioned affinity ; but since in Tnplecta and Triplagia the three spines lie horizontally, they may have changed this original position in different direction, in Plagiacantha and Plectophora becoming divergent upwards, whereas in Plagoniscus and Plectaniscus (as in the Spyroidea and Cyrtoidea) directed downwards.
The triradial structure, common to the Triplagida and Triplectida, is replaced by the quadriradial structure in the Tetraplagida and Tetraplectida. Probably the latter have been derived from the former by development of a fourth spine, and then this latter would correspond to the "apical horn" of the other NASSELLARIA. But possibly also both struc- tures have originated independently from one another. We may distinguish not less than four different kinds of the quadriradial structure. In the first case all four spines are equal, and diverge from a common central point at equal angles in different direc- tions, corresponding to the four axes of a regular tetrahedron (Tetraplagia and Tetraplecta, PL 91, figs. 3, 8).
In the second case all four spines are also equal, but they are not united in a common central point, but opposite in pairs on the two poles of a common central rod (Plagonidium). Therefore the skeleton possesses here the same form as in the " geminate-biradiate " spicula of many Beloidea (e.g., Thalassoxanthium bifurcum and Spheerozoum furcatuni). The development of the short horizontal middle rod, con- necting the two divergent pairs of spines, is here probably effected by the porochora of the central capsule resting upon it.
Whilst in these two cases of quadriradial structure all four spines are equal, in* two other cases they become differentiated in a very remarkable manner. One spine is vertically directed upwards, in shape and size different from the three others, which are directed downwards ; the former corresponding probably to the " apical horn," the latter to the three "basal feet," which are found in the great majority of the Spyroidea
902 THE VOYAGE OF H.M.S. CHALLENGER.
and Cyrtoidea. Therefore we encounter here for the first time that characteristic " cortinar structure " which is complete in Cortina and Cortiniscus (PI. 92, figs. 11—13, 21), and which may be regarded as the strongest argument for a close relationship, or even for a common monophyletic origin of all NASSELLARIA.
The four spines, which we regard therefore as " cortinar spines," exhibit a twofold kind of central junction. In the simpler case they are united in a common central point, on which rests the porochora of the central capsule (Plagoniscus and Plectaniscus, PL 91, figs. 4, 9). These forms are nearer to Cortina, and may be derived immedi- ately from Tetraplagia and Tetraplecta by differentiation of the four equal spines. In the other case the four cortinar spines are separated in pairs, diverging from the two poles of a short horizontal common " central rod " (Plagiocarpa and Periplecta, PI. 91, figs. 5, 10). These forms may be compared with the spicula of some Beloidea and derived from Plagonidium ; but their basal central rod may be compared again with the basal part of the sagittal ring of Cortina, and this comparison becomes. very important in those forms like Plagiocarpa procortina (PI. 91, fig. 5). Here the four spines approach very nearly to those of Cortina; the two ventral spines (or pectoral feet) on the anterior pole of the middle rod are equal, but very different from the two dorsal spines, arising from the posterior pole ; the lower odd spine of the latter corresponds to the " caudal foot," the upper spine to the " apical horn " of Cortina and of the Cyrtellaria. The vertical plane, determined by these two dorsal spines, is the sagittal plane, and two opposite curved branches which lie in this plane (an upper arising from the basal part of the apical spine and a lower arising from the anterior pole of the middle rod) may be regarded as ventral parts of an incomplete sagittal ring. This interesting form and some other similar Tetraplagida may be regarded either as beginning Stephoidea (Cortina, with incomplete sagittal ring) or as retrograde Stephoidea (Cortina, with partly reduced sagittal ring). In every case they seem to indicate the near relationship between the Stephoidea and Plectoidea.
Another argument for this close relationship may be found in the position of the central capsule in the interesting genus Plagiocarpa (PI. 91, fig. 5). Its basal part (with the porochora) rests upon the common central rod, its ventral face upon the ventral prolongation of the latter, its dorsal face upon the apical horn ; its axis lies in the sagittal plane. The three basal spines (the odd caudal and the paired pectoral feet) diverge from its basal pole downwards in the same manner as in the Cortinida, the Zygospyrida and the Monocyrtida.
Less important than those quadriradial Tetraplagida and Tetraplectida, are the sexradial Plectoidea, the Hexaplagida and Hexaplectida. These may be derived immediately from the triradial Plectoidea by prolongation of the three primary original spines (of Plagiacantha) over the common central point. Here also two
REPORT ON THE RADIOLARIA. 903
different kinds of central junction are found. In the simpler case all six radial spines arise from a common central point (Hexaplagia and Hexaplecta). In the other case the six radial spines arise from the two poles of a short horizontal common central rod, opposed in two groups, each of three spines (Plagonium and Plectanium, PL 91, figs. 6, 11). In this latter case the single corresponding spines of the two opposite groups are usually parallel, and exhibit therefore exactly the same characteristic " geminate- triradiate " form which is found in many Beloidea (e.g., in the common Sphcerozoum punctatum and the similar Lampoxanthium punctatum).
The fourth and last group of this suborder contains the multiradiate Plectoidea, the Polyplagida and Polyplectida. Here the number of radial spines, diverging from the common centre, exceeds six, and is commonly seven to nine, at other times ten to twelve or more (Polyplagia and Polyplecta, PL 91, fig. 12). When these two genera are better known from further accurate observations, they may probably be divided into several different genera (as already proposed in my Prodromus, 1881), since not only the number, but also the central junction and the arrangement of the numerous radial spines in the few observed species seems to be very different. In some seven-radiate species (e.g., Polyplecta heptacantha) four larger spines seem to be true " cortinar spines," the three smaller secondary productions of the former. In the nine-radiate species the nine spines seem to be sometimes basal branches of three primary spines, at other times six secondary intercalated between the three primary (like Enneaphormis, PL 57, fig. 9). In those multiradial Plectoidea, in which the number of spines amounts to ten or twelve or more, the laws of disposition are not yet recognised.
Comparing these different productions of the skeleton in the numerous Plectoidea, we find expressed two remarkable and very different affinities. On the one hand many Plectoidea exhibit exactly the same peculiar forms, which are only found besides in the Beloidea (as many species of Triplagia, Plagiacantha, Tetraplagia, Plagonidium, Hexaplagia, and Plagonium). On the other hand many Plectoidea bear the same characteristic composition of the skeleton (or the " cortinar structure ") which is found in the Cortinida among the Stephoidea, and in numerous Spyroidea and Cyrtoidea, which all agree in the possession of three divergent basal feet and a vertical apical horn. A most important argument for the close affinity of all these " cortinar NASSELLAKIA " seems to be given by the fact that the sagittal ring, which in Cortina is combined with the quadriradial structure, exhibits in the Cyrtellaria the most different stages of development; in one group it is complete, in the second incomplete, and in the third it has completely disappeared.
The form of the radial spines composing the skeleton is usually three-sided prismatic, gradually tapering from the thicker central base towards the distal apex ; sometimes they are slender pyramidal. More rarely the spines are cylindrical or slender conical. In the majority of species the spines are straight, in the minority more or
904 THE VOYAGE OF H.M.S. CHALLENGER.
less curved. In very few species only are they quite simple, without branches. They are nearly always more or less branched, in many larger species very richly ramified. The modes of ramification are rather variable. In the majority of Plectoidea the spines are rather regularly verticillate, bearing an increasing number of verticils, each of which is composed of three divergent branches. These arise from the three edges of the spine, and all the branches of one edge are usually parallel, either perpendicular to the spine, or directed at an acute angle towards its apex. When the verticils are numerous (five to ten or more), their size commonly tapers gradually towards the apex. Pinnate spines occur more rarely than verticillate ones ; in this case the two paired lateral edges only of the prismatic spine bear opposite or alternate branches, whilst the odd middle edge bears no ramules. In some species the spines are singly or doubly forked. In many species (mainly those with cylindrical spines) the ramifica- tion of the spines is more or less irregular.
Whilst in all Plagonida the branches of the spines remain perfectly free, in all Plectanida, again, the meeting ends of the branches become united and grow together, and by this concrescence a loose network arises, like wickerwork, which partly encloses the central capsule and the central parts of the spines, on which it rests. The meshes of this loose wickerwork are large, either quite irregular, of very different size and form, or more or less regular, with a certain form and arrangement of the meshes, effected by the peculiar kind of ramification. Commonly the siliceous threads of the arachnoidal wickerwork are very thin, often extremely delicate, representing " pseudopodia metamorphosed into silex." Sometimes the wickerwork is spongy. Its surface is constantly rough and bristly, with free ends of the spine -branches, never covered with a regular lattice-plate, as in the Cyrtellaria (Spyroidea, Botryodea> and Cyrtoidea).
The entire form of the central wickerwork is in the minority of Plectanida quite irregular and indefinite ; in the majority, however, a certain more or less regular entire form is recognisable, effected by a certain, more or less regular origin and mode of the connection of the meeting branches. So in some species of Triplecta (PI. 91, fig. 7) the network represents a triangular plate, of Plectophora and Plectaniscus a three-sided pyramid, of Tetraplecta (PI. 91, fig. 3) a tetrahedron, and in many other species a polyhedron of more or less regular form. Some species of Plectanida become very similar to certain species of Stephoidea, Spyroidea, and Cyrtoidea; so Plectaniscus and Periplecta approach to Cortina and Cortiniscus, Pteroscenium and Olathrocorys, &c. (compare Pis. 92, 93, 53, 64, &c.). They may represent a true phylogenetic connection between both groups. But in these cases also the distinction is determined by the fact that the true Plectoidea never possess a complete sagittal ring (like the Stephoidea) nor a regular lattice-shell (like the Spyroidea, Botryodea, and Cyrtoidea).
REPORT ON THE RADIOLARIA. 905
The Central Capsule of the Plectoidea constantly exhibits the peculiar characters of the MONOPYLEA or NASSELLARIA. It is commonly ovate, more rarely ellipsoidal or even spherical, sometimes conical or lentelliptical. The lower or basal pole of its vertical main axis constantly exhibits the characteristic " porochora " (or the area porosa) of the MONOPYLEA, and upon this rests the peculiar " podoconus " (or the pseudopodial-cone) of this legion. On this porochora the central capsule is in immediate connection with the central point of the skeleton, or the horizontal common central rod, from which the radial spines arise. The endoplasm, or the protoplasm of the central capsule (besides the podoconus), contains commonly one large alveole or several small vacuoles, and often pigment-granules. The nucleus is large, spherical or ovate, and exhibits the same character as in all the other MONOPYLEA ; it encloses usually a single nucleolus.
The position of the central capsule and its topographical relation to the skeleton offers in the different Plectoidea some important and as yet unsolved problems, which can be answered only by fresh and accurate observations on living specimens. In Triplagia, and Triplecta, where the triangular skeleton lies in a horizontal plane, the vertical main axis of the central capsule is perpendicular to the central point of that supporting triangle. In Plagiacantha and Plectophora, where the three radial spines correspond to the edges of a flat pyramid, the capsule is enclosed in the pyramidal space of the latter, its basal pole touching the apex ; therefore in the normal position of the body the three divergent rays are directed upwards. In Tetraplagia and Tetraplecta probably the same position is retained, and therefore the fourth free spine, here developed, is probably directed vertically downwards. In Plagoniscus and Plectaniscus, however, and, moreover, in the closely allied Plagiocarpa and the corres- ponding Periplecta (PI. 91, figs. 5, 10) the position of the central capsule, relative to the skeleton, seems to be inverse, and to agree with that of the Stephoidea (Cortina, Cortiniscus, &c.) and the Cyrtoidea (Pteroscenium, Clathrocorys, &c.); the three divergent spines are here directed downwards (as basal feet), whilst the opposite fourth spine is vertically directed upwards (as an apical horn); the capsule rests here upon the tripod, which lies below it, and is inclined with its dorsal face to the apical spine. In the majority of the other Plectoidea the position of the central capsule and its relation to the skeleton are not yet sufficiently observed, and require further accurate researches. Its position seems to be very different in the several genera. The capsule is never perforated by parts of the skeleton; this latter is constantly extra-capsular.
The physiological value of the skeleton, with regard to the central capsule, is different in the Plagonida and Plectanida; in the former it supports, in the latter it encloses the capsule like a shell. In the Nassellida, where no skeleton is developed, the central capsule is quite free and naked, enveloped only by the calymma.
(ZOOL. CHALL. EXP. PART XL. 1885.) Rr 114
906 THE VOYAGE OF H.M.S. CHALLENGER.
The calymma or the extracapsular jelly -veil in all Plectoidea is ' voluminous, and encloses not only the central capsule completely, but also the skeleton wholly or partially. Its form is of the greatest value for the development and configuration of the skeleton. Sometimes the calymma is alveolate and foamy, as in Nassella and the common Thalassicolla. In several other Plectoidea the calymma seems to include numerous small vacuoles, sometimes also pigment-granules. Xanthellse are commonly scattered in it in great numbers. The pseudopodia, arising in a large bunch from the porochora of the capsule, and running along the branches of the radial spines, seem to be always numerous, richly branched, and with a strong tendency to form anastomoses. The peculiar form of their network is often exactly preserved in the con- formation of the skeleton, produced by them. The peculiarities of this network require further accurate observations, as does the whole organisation of the Plectoidea.
Synopsis of the Families of Plectoidea.
I. Skeleton (originally tripodal) composed of radial spines united in a common
centre and supporting the central capsule, without wicker-work, . .1. PLAGONIDA,
II. Skeleton (originally tripodal) wattled, with irregular wicker-work, composed of the
united branches of radial spines and enveloping the central capsule, . . 2. PLECTANIDA.
Family XL VI. PLAGONIDA, Haeckel.
Plagonida, Haeckel, 1881, Prodromus, p. 423.
Plagiacanthida (sensu strictiori), Eichard Hertwig, 1879, Organismus d. Eadiol., p. 72.
Definition. — P lectoidea with a spiny skeleton, composed of radial spines, which arise from a common central point or central rod, and support the free central capsule.
The family Plagonida comprises those NASSELLARIA in which the skeleton is only composed of united radial spines, arising from a common centre, without any connec- tion of meeting branches of the spines ; the rudimentary skeleton exhibits therefore neither a loose wickerwork (as in the closely allied Plectanida), nor a ring (as in the Stephoidea), nor a complete lattice-shell (as in the Cyrtellaria, the Spyroidea, Botryodea, and Cyrtoidea). The central capsule, which possesses all the characters of the MONOPYLEA, is therefore free, not enclosed, and only on one side supported or partly protected by the radial spines or their branches.
Two species only of Plagonida have been hitherto known. The first form described is the Plagiacantha arachnoides, discovered thirty years ago (1855) by Claparede on the western shore of Norway. Another species of the same genus, from the Mediterranean, was very accurately described by Eichard Hertwig in 1879 in his Organismus der
REPORT ON THE RADIOLARIA. 907
Eadiolarien (Plagiacantha abietina). Upon these two species the latter founded his family Plagiacanthida, a term which was afterwards employed by Biitschli and others, for the whole group of Plectoidea. Many new forms are contained in the collec- tion of the Challenger, so that we may describe here nine genera and thirty-four species.
The family Plagonida may be divided into four different subfamilies, according to the numbers of the radial spines which compose the skeleton : Triplagida with three, Tetraplagida with four, Hexaplagida with six, and Polyplagida with numerous (seven to nine or more) radial spines. These are united commonly in one common central point, upon which rests the basal pole of the central capsule, with the porochora. More rarely (in the genera Plagonidium, Plagiocarpa, and Plagonium) the spines arise in two opposite groups (each with two or three spines) from the two poles of a common central rod; in this case the basal pole of the central capsule with the porochora rests upon the horizontal common rod, which corresponds probably to the basal part of the sagittal ring of the Stephoidea and Cyrtellaria.
The different forms which the skeleton of the Plagonida assumes in the different genera of this family, and the important relations which these exhibit on the one hand to the spicula of the Beloidea, and on the other hand to the shell of some Stephoidea (Cortina, Cortiniscus, &c.) and Cyrtoidea (Pteroscenium, Clathrocorys, &c.), have been already pointed out in the preceding description of the suborder Plectoidea. There it is also demonstrated, that all these different forms may be derived from the simplest triradial forms, Triplagia and Plagiacantha (compare above, pp. 900-904).
Whilst the genera of the Plagonida are characterised by the number of the radial spines and the peculiar mode of junction in a common central point or at the two poles of a common central rod, the different species of this family may be defined by the peculiar form of the spines and their branches. These morphological characters have also been already described above. We repeat here only that the radial spines in the majority of species are three-sided prismatic and verticillate, each verticil commonly with three branches. The distal ends of these branches remain constantly free, and are never united, as is always the case in the following family.
The Central Capsule of the Plagonida exhibits the general characters of all MONOPYLEA (compare above, p. 890). It is commonly ovate or ellipsoidal, with vertical main axis ; on the lower pole of the latter is the porochora (or the " area porosa," from which all pseudopodia radiate). This is in immediate connection with the central point or central rod of the skeleton, in which its radial spines are united. The topographical relation of the supporting skeleton to the central capsule seems to exhibit in the different genera of the Plagonida remarkable differences, as already demonstrated above (p. 905).
908
THE VOYAGE OF H.M.S. CHALLENGER.
I. Subfamily
Triplagida. Three radial spines.
II. Subfamily
Tetraplagida. Four radial spines.
III. Subfamily
Hexaplagida. Six radial spines.
IV. Subfamily
Polyplagida. Numerous radial spines.
Synopsis of the Genera of Plagonida.
Three spines lying in one horizontal plane, .
Three spines corresponding to the edges of a flat pyramid,
{All four spines equal, One apical spine opposed to three basal spines,
Four spines arising in two f A11 four 8Pines e1ual> pairs from the poles of a -< „
common central rod. 1 Ont? aP'f l ^Plne °PP°sed to
[ three basal spines,
Six spines arising from one common central point, .
Six spines arising in two opposite groups from the poles of a common central rod, .....
Numerous (seven to nine or more) radial spines arising from a common centre (either a central point or a branched rod), .
384. Triplagia.
385. Plagiacantha.
386. Tetraplagia.
387. Plagoniscus.
388. Plagonidium.
389. Plagiocarpa.
390. Hexaplagia.
391. Plagonium.
392. Polyplagia.
Subfamily 1. TRIPLAGIDA, Haeckel, 1881, Prodromus, p. 423. Definition. — P lagonida with three radial spines.
Genus 384. Triplagia,1 Haeckel, 1881, Prodromus, p. 423.
Definition. — Plagonida with three radial spines, arising from one common central point and lying in one horizontal plane.
The genus Triplagia and the following closely allied Plagiacantha may be regarded as the simplest and most primitive forms of the Plectoidea, perhaps as the common ancestral stock of this suborder. The skeleton is composed of three simple or branched radial spines, arising from one common central point. These three spines in Triplagia lie in one and the same plane, whilst in Plagiacantha they lie in different planes. Therefore the former exhibits the simplest type of the triradial structure, common to the majority of NASSELLARIA.
1 Triplagia= Triangular or three-radial ;
REPORT ON THE RADIOLARIA. 909
1. Triplagia primordialitt, n. sp. (PL 91, fig. 2).
Spines straight, of equal size and similar form, equidistant, three-sided prismatic, each with two pairs of opposite lateral branches, which are correspondingly parallel to the two other spines ; the proximal branches twice as long as the distal branches.
Dimensions. — Length of each spine O2, of the basal branches 0'07.
Habitat. — Central Pacific, Station 271, depth 2425 fathoms.
2. Triplagia triradialis, n. sp.
Spines straight, of equal size and similar form, equidistant, three-sided prismatic, regularly pin- nate, with six pairs of opposite pinnulse, tapering gradually towards the distal ends ; the basal pinnulse are again branched, with straight ramules.
Dimensions. — Length of each spine 0'27, of the basal branches 0'08.
Habitat. — North Pacific, Station 256, surface.
3. Triplagia horizontalis, n. sp.
Spines curved, cylindrical, irregularly branched, with- three primary and nine to twelve secondary branches, which are also slightly curved. The angles between the bases of the three spines are equal, but the size and form of the branches different.
Dimensions. — Length of the three spines 0'15 to 0'25, of the basal branches 0'05 to 0'08.
Habitat. — West Tropical Pacific, Station 225, depth 4475 fathoms.
Genus 385. Plagiacantha,1 Claparede, 1856, Monatsber. d. k. preuss. Akad. d. Wiss. Berlin, November 13.
Definition. — Plagonida with three radial spines, arising from one common central point and corresponding to the edges of a three-sided pyramid.
The genus Plagiacantha agrees with the preceding Triplagia in the simple structure of the triradial skeleton, composed of three diverging radial spines, which are united in a common centre at the oral pole of the central capsule. But whilst the three radial rods of Triplagia lie in one horizontal plane, here they lie in different planes and correspond to the three edges of a flat pyramid. Plagiacantha arachnoides, described in 1856 by Claparede, was the earliest known form of all Plectoidea.
1 Plagiacantha = Having spines on the sides ; ***y/of, «x«»9a-
910 THE VOYAGE OF H.M.S. CHALLENGES.
1. Plagiacantha arachnoides, Claparfede.
Plagiacantha arachnoides, Claparede, 1856, Monatsber. d. k. preuss. Akad. d. Wiss. Berlin,
November 13. Plagiacantha arachnoides, Claparede, 1858, Etudes sur les Infusoires et les Rhizopodes, p. 462
(pL xxii. fig. 8). Acanthometra arachnoides, Claparede, 1855, Monatsber. d. k. preuss. Akad. d. Wiss. Berlin, p. 675.
Spines straight, cylindrical, divided into three divergent straight branches of equal size ; each branch two to three times as. long as the simple thicker basal part.
Dimensions. — Length of the spines 012 to 0'2, of the branches O08 to 014. Habitat. — North Atlantic, coast of Norway, Claparede, surface.
2. Plagiacantha furcata, n. sp.
Spines straight, cylindrical, divided into two divergent straight branches of equal size, of about the same length as the simple basal part. The spines and their branches are smooth. Dimensions. — Length of the spines 0'24, of their fork-branches 012. Habitat. — North Pacific, Station 254, surface.
3. Plagiacantha dodecantha, n. sp.
Spines straight, three-sided prismatic, in the middle with one verticil composed of three divergent straight branches of equal size, of about the same length as the simple basal part. The edges of the spines and their branches are thorny.
Dimensions. — Length of the spines 0'24, of the branches 01.
Habitat. — Central Pacific, Station 274, surface.
4. Plagiacantha abietina, Richard Hertwig.
Plagiacantha abietina, Richard Hertwig, 1879, Organjsmus d. Radiol., p. 72, Taf. vii. figs. 6-6J.
Spines straight, three-sided prismatic, with three verticils of three divergent straight lateral branches, decreasing in size towards the distal end ; the branches of the first verticil about twice as long as those of the second, and four times as long as those of the third verticil. All nine branches of each spine simple, straight, three-sided pyramidal.
Dimensions. — Length of the spines 0'2 to 0'3, of the basal branches O'OG to 0'08.
Habitat. — Mediterranean, Messina (R Hertwig), surface.
5. Plagiacantha verticillata, n. sp.
Spines curved, three-sided prismatic, with six to nine verticils of three divergent branches, decreasing in size towards the distal end ; the branches of the first verticil about twice as long as those of the fourth verticil. All branches simple, slightly curved, bristle-shaped.
Dimensions. — Length of the spines 0'27, of the basal branches 012.
Habitat. — South Pacific, Station 296, surface.
REPORT ON THE RADIOLARIA. 911
i
6. Plagiacantha elatine, n. sp.
Spines straight, three-sided prismatic, with prominent wing-like edges and ten to twelve verticils of three divergent branches, decreasing in size towards the distal end ; the branches of the three or four basal verticils are again ramified and much larger than the simple branches of the distal verticils.
Dimensions. — Length of the spines O36, of the basal branches 014.
Habitat. — Central Pacific, Station 268, depth 2900 fathoms.
Subfamily 2. TETRAPLAGIDA, Haeckel, 1881, Prodromus, p. 424. Definition. — P lagonida with four radial spines.
Genus 386. Tetraplagia,1 Haeckel, 1881, Prodromus, p. 424.
Definition. — P lagonida with four equal radial spines, arising from one common central point, and corresponding to the four axes of a tetrahedron.
The genus Tetraplagia is one of the most important Plectoidea, and possibly the common ancestral form of many NASSELLAEIA (compare above, p. 901). The skeleton is composed of four radial rods, diverging from one common centre in different directions, and corresponding to the four axes, which extend from the central point of a tetrahedron to the central points of its four faces. The whole skeleton of Tetraplagia exhibits therefore the same form, which is observed in the single quadriradiate spicula of some Beloidea (in some species of Lampoxanthium, Spharozoum, &c.).
1. Tetraplagia geometrica, n. sp.
Spines straight, cylindrical, perfectly equal, corresponding in regular disposition exactly to the four geometrical axes of a regular tetrahedron ; in the middle arise from each spine two opposite equal lateral branches of half the length of the spine.
Dimensions. — Length of the spines 012, of the branches 0'06.
Habitat. — Central Pacific, Station 266, surface.
2. Tetraplagia phcenaxonia, n. sp. (PL 91, fig. 3).
Spines straight or slightly curved, three-sided prismatic, with irregular short branches arising from the three edges ; the branches are thorny, tapering towards the apex. Dimensions. — Length of the spines 015, of the basal branches 0'03. Habitat. — Tropical Atlantic, Station 332, surface.
1 Tetraplagia = Four-sided ; re-rj cnrA«y/oj.
912 THE VOYAGE OF H.M.S. CHALLENGER.
3. Tetraplagia dbietina, Haeckel.
Plagiacantha dbietina, var. quadrispina, Kichard Hertwig, 1879, Organismus d. Eadiol., p. 73.
Spines straight, three-sided prismatic, verticillate, with six to eight verticils of three simple straight branches ; the branches of each edge are parallel, tapering towards the distal end. R Hertwig regards this species only as a four-spined variety of his three-spined Plagiacantha abietina ; but a specimen, observed by me in Corfu, exhibited all the characters of Tetraplagia.
Dimensions. — Length of the spines 0'2, of the basal branches 0'07.
Habitat. — Mediterranean (Messina, Corfu), surface.
Genus 387. Plagoniscus,1 n. gen.
Definition. — P lagonida with four unequal radial spines, arising from one common central point ; one vertical or apical spine opposed to three divergent or basal spines.
The genus Plagoniscus agrees with the preceding Tetraplagia (its probable ancestral form) in the possession of four radial spines, diverging from one common central point. But whilst in this latter all four spines are equal, corresponding exactly to the four axes of a tetrahedron, here in Playiocarpa an important .difference exists between one vertical or apical spine and three other divergent basal spines ; these latter corresponding probably to the three " feet," the former to the single " apical horn " of the majority of NASSELLARIA. Perhaps we find here one of the oldest and simplest types of their " triradial or cortinar structure " (compare above, p. 902).
1. Plagoniscus tripodiscus, n. sp. (PL 91, fig. 4).
Spines three-sided prismatic, thorny. Apical spine nearly straight, verticillate, with four to five verticils of three thorny branches, tapering towards the apex. Three basal spines somewhat shorter, curved, with three thorny edges.
Dimensions. — Length of the apical spine 0'2, of the basal spines 015.
Habitat. — Central Pacific, Station 263, surface.
2. Plagoniscus euscenium, n. sp.
Spines three-sided prismatic, thorny, with dentate edges, and three to six verticils of three short branches. Apical spine straight, with six verticils, nearly twice as long as the three curved basal spines, each of which bears three verticils ; the basal verticils larger and ramified. Eesembles somewhat Euscenium eucolpium, PI. 53, fig. 12, but has no latticed shell.
Dimensions. — Length of the apical spine 0'3, of the basal spines 0'16.
Habitat. — North Pacific, Station 247, surface.
1 Plagoniscus — Side — windlass ;
REPORT ON THE RADIOLARIA. 913
3. Plagoniscus cortinaris, n. sp.
Spines three-sided prismatic, straight, verticillate. Apical spine with twelve verticils, one and a half times as long as the three basal spines, each of which bears eight verticils of three branches. The branches are also prismatic, straight, on each edge parallel, tapering towards the apex, hi the three basal spines forked, in the apical spine more branched. Similar to the cortinar skeleton of Clathrocorys (PL 64, figs. 8-10).
Dimensions. — Length of the apical spine 0'24, of the basal spines 016.
Habitat. — South Atlantic, Station 338, surface.
4. Plagoniscus nassellaris, n. sp.
Spines cylindrical, curved, irregularly branched. Apical spine half as long as, and less branched than the three basal spines, which are sigmoidal, nearly horizontally expanded in the proximal half, descending in the distal half.
Dimensions. — Length of the apical spine 01, of the three basal spines 018.
Habitat. — West Tropical Pacific, Station 224, surface.
Genus 388. Plagonidium,^ Haeckel, 1881, Prodromus, p. 424.
Definition. — P lagonida with four equal radial spines, arising in pairs from the two poles of a common central rod.
The genus Plagonidium and the following Plagiocarpa possess four radial spines, like the two preceding genera. But whilst the four rods in these latter arise from a common centre, here they arise in two pairs from the two poles of a common middle rod ; they have therefore exactly the same form which we find in the single spicula of some Beloidea (e.g., Thalassoxanthium furcatum, Spharozoum furcatum, &c.). Probably the middle rod is horizontal and serves as supporting base for the central capsule, whilst two opposite spines are directed upwards, two other downwards.
1. Plagonidium bigeminum, n. sp.
Spines straight, three-sided prismatic, four to six times as long as the common central rod, pinnate, with four to five pairs of opposite pinnulse, the distal of which are simple, the proximal again branched.
Dimensions,— Length of the spines 016, of the middle rod 0'032.
Habitat. — Indian Ocean, Sunda Strait (Rabbe), surface.
1 Plagonidium = Small side-article ; •jr^ttyuni^ioii. CHALL. EXP. — PART XL. — 1886.) :Rr 115
914 THE VOYAGE OF H.M.S. CHALLENGER.
2. Plagonidium quadrigeminum, n. sp.
Spines cylindrical, curved, eight to ten times as long as the common central rod, in the distal half forked ; the fork -branches curved, somewhat longer than the basal part. Dimensions. — Length of the spines 018, of the middle rod 0'02. Habitat. — Antarctic Ocean, Kerguelen Island, Station 159, surface.
Genus 389. Plagiocarpa,1 Haeckel, 1881, Prodromus, p. 424.
Definition. — P lagonida with four unequal radial spines, arising in pairs from the two poles of a common central rod ; one ascending apical spine opposed to three descending basal spines.
The genus Plagiocarpa agrees with the preceding Plagonidium in the possession of a common horizontal middle rod, the two poles of which bear two pairs of divergent spines; but whilst in the preceding all four spines are equal, here they are differentiated in the same manner as in Plagoniscus, which differs only in the absence of the middle rod. The two observed and closely allied species of this genus are of peculiar interest, since they belong possibly to the common ancestral forms of the NASSELLAEIA ; the basal middle rod corresponds perhaps to the basal part of a sagittal ring, the apical spine to its dorsal part, the three other spines to the basal feet (compare above, p. 902).
1. Plagiocarpa procortina, n. sp. (PI. 91, fig. 5).
Spines cylindrical, curved, thorny, three to four times as long as the common middle rod. Apical spine and the meeting caudal spine (or the posterior basal spine) somewhat larger and with more numerous thorns than the two paired pectoral (or anterior) spines. From the common base of the latter arises an anterior prolongation of the horizontal middle rod, which m the sagittal plane is curved upwards and corresponds to the sternal foot of many Cyrtellaria. An ascending branch of this spine is opposed to a descending branch of the apical spine, both together forming an incomplete sagittal ring.
Dimensions. — Length of the two larger spines 0'15, of the two smaller 0'12.
Habitat. — Mediterranean (Portofino near Genoa), surface.
2. Plagiocarpa procyrtella, n. sp.
Spines of form and arrangement similar to those of the preceding species, but longer and more
branched, six to eight times as long as the shorter common middle rod. The two characteristic
1 Plagiocarpa = Having its fruit (the central capsule) on the side ;
EEPORT ON THE RADIOLARIA. 915
opposed branches (the ascending branch of the basal rod and the descending branch of the apical spine), which in the preceding species nearly compose a sagittal ring, are here absent.
Dimensions. — Length of the two larger 0'27, of the two smaller 0'21.
Habitat. — North Atlantic, Iceland (Steenstrup), surface.
Subfamily 3. HEXAPLAGIDA, Haeckel. Definition. — P lagonida with six radial spines.
Genus 390. Hexaplagia,1 Haeckel, 1881, Prodromus, p. 424.
Definition. — P lagonida with six radial spines, arising from one common central point.
The genus Hexaplagia differs from the preceding genera of Plagonida in the possession of six radial spines, diverging from one common central point. Commonly, these six spines seem to lie opposite in pairs in three different meridian planes, and in this case Hexaplagia may be regarded as a Plagiacantha, the three radial spines of which are prolonged over the basal pole of the central capsule. But in other species the six spines seem to lie in different planes. Further observations are required.
1. Hexaplagia arctica, n. sp.
Spines opposite in pairs in three diameters, crossed in the common centre, straight, three-sided prismatic, with dentate edges. The three pairs are equal, but the upper spine of each pair only half as long as the lower spine.
Dimensions. — Length of the upper spine 0'13, of the lower 0'27.
Habitat. — Arctic Ocean (Greenland), in the stomach of a Medusa (Olrik).
2. Hexaplagia antarctica, n. sp.
Spines opposite in pairs in three diameters, crossed in the common centre, slightly curved, three- sided prismatic, with verticillate branches ; the three pairs are equal, but the lower spine of each pair bears three to four verticils, each of three branches, and is two to three times as long as the upper spine, which bears two verticils only.
Dimensions. — Length of the upper spine 012, of the lower 0'3.
Habitat. — Antarctic Ocean, Station 157, depth 1950 fathoms.
1 Hexaplagia = Six-si Jed ;
916 THE VOYAGE OF H.M.S. CHALLENGER.
3. Hexaplagia collar is, n. sp.
Spines in opposite pairs in three diameters, crossed in the common centre, straight, cylindrical, pinnate, with three to four pairs of opposite lateral branches or regular pinnulas. All six spines are equidistant, of equal size and similar form, and lie with their branches nearly in one horizontal plane. Therefore they are similar to the six radial rods in the collar septum of many Spyroidea and Cyrtoidea (e.g., Calpophcena, PI. 53, fig. 18).
Dimensions. — Length of all six spines 0'18, of their basal pinnulse 0'04.
Habitat. — East of New Zealand, Station 169, surface.
4. Hexaplagia australis, n. sp.
Spines unequal, at unequal intervals, not opposite in pairs, cylindrical, irregularly branched and curved. In this species a definite arrangement of the six different spines could not be detected. Dimensions. — Length of the spines 0'2 to 0'3, of their largest branches 01. Habitat. — South of Australia, Station 160, surface.
Genus 391. Plagonium,1 Haeckel, 1881, Prodromus, p. 423,
Definition. — P lagonida with six radial spines, arising in two opposite divergent groups from the two poles of a common central rod.
The genus Plagonium differs from the preceding closely allied Hexaplagia in the remarkable peculiarity, that the six radial spines do not arise from one common central point, but from the two poles of a common horizontal middle rod ; three divergent spines on each pole. The skeleton of Plagonium exhibits therefore the same remark- able form which is found in the isolated spicula of numerous Beloidea (e.g., Lampoxanthium punctatum, Sphcerozoum punctatum), and bears the same relation to Hexaplagia that Plagonidium does to Tetraplagia.
1. Plagonium sphcerozoum, n. sp. (PL 91, fig. 6).
Spines straight and stout, three-sided prismatic, about twice as long as the common middle rod, irregularly branched or nearly verticillate, with short thorny branches. Similar to the single spicula of some species of Sphcerozoum and Lampoxanthium.
Dimensions. — Length of the spines 012, of the middle rod 0'06.
Habitat. — Equatorial Atlantic, Station 347, surface.
1 Plagonium = Side-article ;
REPORT ON THE RADIOLARIA. 917
2. Plagonium lampoxanthium, n. sp.
Spines irregularly curved, slender, cylindrical, six to eight times as long as the common middle rod, in the proximal half smooth, in the distal half covered with short thorns. (Similar to an isolated spiculum of Lampoxanthium punctatum or of Sphcerozoum variabite, PL 4 fig. 5.)
Dimensions. — Length of the spines 018, of the middle rod 0'03.
Habitat. — North Pacific, Station 240, surface.
3. Plagonium arborescens, n. sp.
Spines irregularly curved and branched, slender, cylindrical, thorny, twelve to sixteen times as long as the middle rod ; the branches are large, arborescent, their ramules again ramified and very thorny.
Dimensions. — Length of the spines 0'2 to 0'25, of the middle rod 0'02.
Habitat. — Indian Ocean, Madagascar (Eabbe), surface.
4. Plagonium trigeminum, n. sp.
Spines straight, slender, cylindrical, four to six times as long as the middle rod, in the basal half smooth, in the distal half arborescent, with three to four irregular verticils of ramified branches. (Similar to a single spiculum of Sphcerozoum verticillatum, PL 4, fig. 7.)
Dimensions. — Length of the spines 015 to 0'2, of the middle rod 0'05.
Habitat. — Central Pacific, Station 265, depth 2900 fathoms.
5. Plagonium distriactis, n. sp.
Spines straight and stout, three-sided prismatic, smooth, ten to twelve times as long as the middle rod ; each on the distal end cleft into three divergent straight branches, which are again trichotomous.
Dimensions. — Length of the spines 015 to 018, of the middle rod 0'015.
Habitat. — South Pacific, Station 288, surface.
Subfamily 4. POLYFLAGIDA, Haeckel, 1881, Prodromus, p. 424. Definition. — P lagonida with numerous (seven to nine or more) radial spines.
Genus 392. Polyplagia,1 n. gen.
Definition. — P lagonida with numerous (seven to nine or more) radial spines, arising from a common centre and lying in different planes.
1 Polyplagia — Manifold;
918 THE VOYAGE OF H.M.S. CHALLEJSTGEK.
The genus Polyplagia alone represents the small subfamily of Polyplagida, dis- tinguished from the other Plagonida by the multiplication of the radial spines, the number of which amounts to seven to nine or more. This increased number is commonly the result of an intercalation of new spines between the three or four primary spines ; it is sometimes also effected by stronger development of branches of the latter, which become independent. The following five species of this genus are very different, require further investigation, and perhaps represent different genera: —
1. Polyplagia septenaria, n. sp.
Seven radial spines, straight, three-sided prismatic, verticillate, of different sizes ; four larger spines correspond to the four axes of a tetrahedron (running from the centre to the four corners), each with five to six verticils of three simple slender branches ; one of these four main spines seems to be the apical, the three others the basal spines of Plagiocarpa ; in the three meridian planes between the latter and the former lie the three smaller spines, diverging upwards, each with two to three verticils. (Similar to Polyplecta heptacantha, PI. 91, fig. 12, but without connection between the branches.)
Dimensions. — Length of the four major spines 0-26, of the three minor Oil.
Habitat. — Central Pacific, Station 274, surface.
2. Polyplagia octonaria, n. sp.
Eight radial spines, straight, three-sided prismatic, of equal size, arising in two opposite groups from the two poles of a short common middle rod (as in SpJwcrozoum arlorescens, PL 4, fig. 8, and in other B e 1 o i d e a). The four spines of each group are divergent, six to eight times as long as the middle rod, each spine armed with three to four verticils of thorny branches.
Dimensions. — Length of the spines 0'15, of the middle rod 0'022.
Habitat. — Indian Ocean, Cocos Islands (Eabbe), surface.
3. Polyplagia novenaria, n. sp.
Nine radial spines of equal size, straight, cylindrical, lying nearly in a horizontal plane, or forming a very flat pyramid. Near the common central point every three spines arise from a short common rod, so that the centre of the skeleton is triradial. Each spine bears towards the apex two divergent straight lateral branches. This species may have been derived from Plagiacantha arach- noides by shortening and reduction of the basal parts of the three original branched primary spines.
Dimensions. — Length of the nine spines 0'24, of the three basal rods 0'02.
Habitat. — North Atlantic, Faeroe Channel (Gulf Stream), John Murray, surface.
4. Polyplagia duodenaria, n. sp.
Twelve radial spines of equal size, arising from a common central point, and diverging in different directions. The twelve spines are very large, opposite in six pairs, cylindrical, longitudinally
REPORT ON THE RADIOLARIA. 919
striped (the expression of concentric lamellae), and with spinulate surface, covered with innumerable small thorns. The basal quarter of each spine is straight and simple, the second quarter twice forked, and these four fork-branches are again in the outer half of the spine richly forked or ramified, with diverging, slightly curved thin branches ; each of the twelve spines with about sixty to eighty terminal branches, the ends of which seem to fall into a spherical face. The position of this remarkable species in this family is doubtful
Dimensions. — Length of the spines 012 to 016, of the simple basal part 0'04.
Habitat. — South Pacific (off Juan Fernandez), Station 299, surface.
5. Polyplagia viminaria, n. sp.
Numerous (sixteen to twenty or more) radial spines of about equal size, arising from a common central point and diverging in different directions, richly and more or less irregularly branched. The ends of the numerous small branches seem to fall into a spherical face. The large spines of this species have the same form and structure as in the preceding, nearly allied species, but are more numerous and more irregularly branched and disposed.
Dimensions. — Length of the spines 0'2 to 0'25, of the simple basal part 0'05.
Habitat. — North Pacific, Station 241, surface.
Family XL VII. PLECTANIDA, Haeckel.
Plectanida, Haeckel, 1881, Prodromus, p. 424.
Definition. — P lectoidea with a wattled skeleton, composed of the meeting and united branches of radial spines, which arise from a common central point or central rod, and protect the partly enclosed central capsule.
The family Plectanida comprises those NASSELLARIA in which the skeleton is composed of radial spines, arising from a common centre, and of a loose wickerwork, produced by concrescence of the meeting branches of those spines. This rudimentary wattled skeleton is either quite irregular or only slightly regular, but it never assumes the form of a complete lattice-shell, as in the Cyrtellaria (the Spyroidea, Botryodea, and Cyrtoidea), nor does it exhibit a ring (as in the Stephoidea). The central capsule is partly or wholly protected, and often entirely enclosed by the wattled skeleton.
Three species only of Plectanida have been hitherto known. The first described form is Plectophora arachnoides, which its discoverer Claparede observed in a living state in 1855 on the western coast of Norway, and considered as a mere variety of his Plagia- cantha arachnoides. Two other species were afterwards observed in the Mediterranean, Polyplecta dumetum, 1856, by Johannes Miiller (united by him with Acanthodesmia) and Polyplecta polybrocha by myself in 1864. Many new forms are found in the
920 THE VOYAGE OF H.M.S. CHALLENGER.
collection of the Challenger, so that we may here distinguish eight genera and twenty- seven species.
The family Plectanida may be divided into four different subfamilies, according to the number of the radial spines which compose the skeleton. These four subfamilies, as also the genera contained in them, correspond exactly to the four subfamilies of Plagonida, from which they have originated : Triplectida with three, Tetraplectida with four, Hexaplectida with six, and Polyplectida with numerous (seven to nine or more) radial spines. These spines are usually united (as in the corresponding ancestral Plagonida) in one common central point, upon which rests the basal pole of the central capsule, with the porochora. More rarely (in the genera Periplecta and Plectanium) the spines arise in two opposite groups (each of two or three spines) from the two poles of a common horizontal central rod, which supports the overlying porochora of the central capsule.
The different genera of Plectonida, which are enumerated in the following synopsis, correspond so exactly to the different genera of Plagonida described above, that probably each of the former has arisen from a corresponding genus of the latter. The only difference between the two is, that in all Plagonida the branches and ramules of the radial spines end freely, without growing together, whilst in all Plectanida the meeting ends of the neighbouring spines grow together and so produce a loose and irregular wickerwork. Therefore the latter constantly possess meshes, which are missing in the former. As soon as any form of Plagonida begins to produce meshes by concrescence of meeting branches of the spines, it passes over into a corresponding form of Plectanida. The loose wickerwork or wattlework so produced is sometimes very irregular, at other times more or less regular ; but it never assumes the regular form of a complete lattice-shell, as in the Cyrtellaria (Spyroidea, Botryodea, and Cyrtoidea). The general differences which this wickerwork exhibits in the different genera of Plectanida have been already described above (compare pp. 900—904).
The Central Capsule of the Plectanida agrees perfectly with that of the ancestral Plagonida, as well in general form and structure as in the peculiar topographical relation to the radial spines (compare above, p. 905). A slight difference between the two families is effected by the higher development of the skeleton in the Plectanida. Since the branches of the radial spines in this family become united and form a loose wicker- work, the central capsule becomes more or less enclosed by the latter, and more perfectly protected, than in the Plagonida, where the branches remain free. In this respect the Plectanida approach more nearly to the Cyrtoidea with which they are connected by such transitional forms as Plectaniscus .and Periplecta on the one hand, Cladoscenium and Pteroscenium on the other.
REPORT ON THE RADIOLARIA.
921
I. Subfamily
Triplectida. Three radial spines.
II. Subfamily
Tetraplectida. Four radial spines.
III. Subfamily
Hexaplectida. Six radial spines.
IV. Subfamily
Polyplectida. Numerous radial spines.
Synopsis of the Genera of Plectanida. Three spines lying in one horizontal plane, . Three spines corresponding to the edges of a flat pyramid,
{All four spines equal, One apical spine opposed to three basal spines,
Four spines arising in two pairs from the poles of a common central rod; one apical spine different from three basal spines, .......
Six spines arising from one common central point, .
Six spines arising in two opposite groups from the poles of a common central rod, .....
Numerous (seven to nine or more) radial spines arising from a common centre (either a central point or a branched rod), .......
393. Triplecta.
394. Plectophora.
395. Tetraplecta.
396. Plectaniscus.
397. Periplecta.
398. Hexaplecta.
399. Pledanium.
400. Polyplecta.
Subfamily 1. TKIPLECTIDA, Haeckel, 1881, Prodromus, p. 424. Definition. — P lectanida with three radial spines.
Genus 393. Triplecta,1 Haeckel, 1881, Prodromus, p. 424.
Definition. — P lectanida with three radial spines, arising from one common central point and lying in one horizontal plane.
The genus Triplecta is the simplest and most primitive of the Plectanida, and may therefore be regarded as the prototype of this family. The skeleton represents a triangular lattice-plate with three radial beams. On the central union of the latter rests the oral pole of the central capsule. Since the axis of the latter is vertical, the lattice-plate must be horizontal, serving for the expansion of the pseudopodia. Triplecta has arisen from Triplagia by union of the branches of its three radial spines. In the simplest case only three large meshes are formed, corresponding prob- ably to the three cortinar meshes in the collar septum of many Cyrtellaria.
1. Triplecta triangulum, n. sp.
Spines straight, equal, smooth, cylindrical, each in the basal half with one pair of divergent straight lateral branches. The opposed branches of every two neighbouring spines are united by a
1 Triplecta = Hunting net with three beams ; TJ/J, TXSXTIJ.
(ZQOL. CHALL. EXP. PABT XL. — 1886.) Rr 116
922 THE VOYAGE OF H.M.S. CHALLENGER.
thin convex bow. In this way arises a very simple, equilateral triangular skeleton, with three equal large meshes.
Dimensions. — Length of the spines 014, sides of the triangle 016.
Habitat. — Tropical Atlantic, Station 348, depth 2450 fathoms.
2. Triplecta triactis, n. sp. (PL 91, fig. 7).
Spines straight, equal, three-sided prismatic, pinnate, each with three to four pairs of opposite slender pinnulse or lateral branches ; the pinnules of each spine are correspondingly parallel to the main rods of the other two spines. All pinnulse branched and connected by a few slender bows, marking the sides of a regular triangle.
Dimensions. — Length of the spines 015, sides of the triangle 017.
Habitat.— Central Pacific, Station 272, depth 2600 fathoms.
Genus 394. Plectophora,1 Haeckel, 1881, Prodromus, p. 424.
Definition. — P lectanida with three radial spines, arising from one common central point and corresponding to the edges of a three-sided pyramid.
The genus Plectophora has been derived from Plagiacantha by union of the meeting neighbouring branches of the three radial spines, and exhibits therefore to it the same relation that Triplecta bears to Triplagia. The loose framework so produced corre- sponds to the three sides of a flat pyramid and supports the central capsule.
\
1. Plectophora triomma, n. sp.
Spines equal, straight, three-sided prismatic, thorny, connected by three convex bows, the meeting branches of lateral spines arising in one pair from the middle part of each spine. There- fore the skeleton exhibits three large ovate meshes only.
Dimensions. — Length of the spines 012, of the meshes 0'08.
Habitat. — North Pacific, Station 238, surface.
2. Plectophora arachnoides, Haeckel.
Plagiacantha arachnoides, var., Claparfede, 1858, Etudes sur les Infusoires et les Ehizopodes, p. 462, Taf. xxii. fig. 9.
Spines straight, cylindrical, trifid, with one pair of lateral branches. The nine diverging, straight, and smooth branches are connected in the distal part by slender concave bows, so that the whole skeleton exhibits nine wide meshes, three larger pentagonal and six smaller triangular.
Dimensions.— Length of the spines 014, of their branches 0P07.
Habitat. — North Atlantic, west coast of Norway (Claparede), surface. 1 Plectophora = Bearing a hunting net ;
REPORT ON THE RADIOLARIA. 923
3. Plectophora novena, n. sp.
Spines slightly curved, three-sided prismatic, thorny, with two pairs of lateral branches. The six smaller distal branches end freely, whilst the six larger basal branches are connected by slender convex bows. There are therefore nine wide meshes, as in the preceding closely allied species.
Dimensions. — Length of the spines 0'18, of the basal branches 0'08.
Habitat. — North Atlantic, Fserb'e Channel (Gulf Stream) (John Murray), surface.
4. Plectophora pyramidalis, n. sp.
Spines straight, three-sided prismatic, with three to four verticils of short lateral branches. The branches of the basal verticils are again ramified, and form by connecting bows a delicate loose framework, covering the three sides of a flat^ pyramid, the three edges of which are the three radial spines.
Dimensions. — Length of the spines 0'2, base of the pyramid 016.
Habitat. — Central Pacific, Station 267, surface.
Subfamily 2. TETRAPLECTIDA, Haeckel, 1881, Prodromus, p. 424. Definition. — P leetanida with four radial spines.
Genus 395. Tetraplecta,1 Haeckel, 1881, Prodromus, p. 424.
Definition. — P leetanida with four equal radial spines, arising from one common central point and corresponding to the four axes of a tetrahedron.
The genus Tetraplecta has been derived from Tetraplagia by union of the neighbour- ing branches of the four radial spines, diverging from a common point in different directions. In some forms of this genus the four rods seem to correspond exactly to the four axes, which are directed from the centre of a tetrahedron towards its four corners ; whilst in other forms the four rods and the angles between them are perhaps not perfectly equal.
1. Tetraplecta tetrahedra, n. sp.
Spines straight, equal, three-sided prismatic, pinnate, each with three or four pairs of opposite
straight slender pinnulae or lateral branches ; the pinnulae of each side are correspondingly parallel.
1 Tetraplecta = Hunting net with four beams ;
924 THE VOYAGE OF H.M.S. CHALLENGER.
All pinnulse connected by a few slender bridges, thus producing a delicate network with irregular rhomboidal meshes.
Dimensions. — Length of the spines 0'15, of the basal branches 0'05.
Habitat. — Central Pacific, Station 272, depth 2600 fathoms.
2. Tetraplecta quadricornis, n. sp.
Spines in the basal half straight, in the distal half slightly curved and irregularly branched, with two to three pairs of unequal alternate lateral branches) the distal ends of which are connected by a few slender bows, marking the six edges of an irregular tetrahedron.
Dimensions. — Length of the spines 0'22, of the basal branches 0'14.
Habitat. — Central Pacific, Station 266, depth 2750 fathoms.
3. Tetraplecta pinigera, n. sp. (PI. 91, fig. 8).
Spines three-sided prismatic, straight, or in the basal half slightly curved, verticillate ; each spine with six to eight three-branched regular verticils, tapering gradually towards the distal end. All branches of each spine lie parallel in three equidistant meridian planes, and are connected by delicate parallel threads, perpendicular to the branches. Therefore the skeleton consists of four pine-shaped trees and twelve delicate triangular wings with rectangular meshes.
Dimensions. — Length of the spines 0-25 to 0'3, of the basal branches 01 to 0-15.
Habitat.— Central Pacific, Station 271, surface.
Genus 396. Plectaniscus,1 nov. gen.
Definition. — P lectanida with four unequal radial spines, arising from one common central point ; one vertical or apical spine opposed to three divergent or basal spines.
The genus Plectaniscus has probably been derived from Plagoniscus by reticular union of the neighbouring branches of the four radial spines, and exhibits therefore to it the same relation that Tetraplecta bears to Tetraplagia. Whilst in these two latter genera the four spines are equal, in the two former genera there is an important differ- ence between a vertical spine (or apical horn) and three divergent (commonly larger) spines, corresponding to the three basal feet of the triradiate NASSELLARIA. Perhaps, therefore, Plectaniscus is one of the remotest ancestors of the latter ; but differs in the absence of a complete lattice-shell.
1 Plectaniscus = Shell of wickerwork ;
REPORT ON THE RADIOLARIA. 925
1. Plectaniscus cortiniscus, n. sp. (PI. 91, fig. 9).
Spines straight, three-sided prismatic, with three to four verticils of short perpendicular branches ; the branches of the distal verticils are simple and free, those of the proximal verticils again ramified and connected by an arachnoidal network of delicate threads. The vertical apical spine (or horn) is scarcely one-third or half as long as the three divergent basal spines (or feet), and the angle between it and the latter is smaller.
Dimensions. — Length of the apical spine 0'05 to 01, of the three basal spines 018 to 0'2.
Habitat. — North Pacific, Station 244, surface.
2. Plectaniscus tripodiscus, n. sp.
Spines curved, cylindrical, with a variable number of irregular branches, which in the distal half of the spines are free, in the basal half again ramified and connected by a loose spongy frame- work. The apical spine is shorter and simpler, nearly straight, less ramified.
Dimensions. — Length of the apical spine 01, of the three basal spines 015 to 018.
Habitat. — North Pacific, Station 238, surface.
3. Plectaniscus archiscenium, n. sp.
Spines slightly curved, three-sided prismatic, with two to three verticils of short curved branches. The vertical apical spine is about twice as long as the three basal spines, and connected with them by an irregular loose framework. The three basal spines are connected together only by a simple ring, so that between them remain three large collar holes, like those of the similar and closely allied Archisceniwn yuadrispinum (PL 53, fig. 11).
Dimensions. — Length of the apical spine 0'32, of the three basal spines 018.
Habitat. — South Pacific, Station 295, depth 1500 fathoms.
4. Plectaniscus cladoscenium, n. sp.
Spines curved, three-sided prismatic. The three basal spines pinnate, with four to five pairs of opposite curved pinnulae ; the distal pairs are simple and free, the basal pairs branched and connected by an irregular delicate framework, which together with the apical spine forms a spongy cap-shaped shell, similar to Cladoscenium. Apical spine about half as long, simple.
Dimensions. — Length of the apical spine 01, of the three basal spines 018.
Habitat. — Central Pacific, Station 274, surface.
5. Plectaniscus clathrocorys, n. sp.
Spines straight, three-sided prismatic, with seven or eight verticils of ramified branches, which in the basal half are connected by an irregular loose framework. In the distal half each of the three divergent basal spines (or feet) is connected with the longer apical spine (or horn) by a
926 THE VOYAGE OF H.M.S. CHALLENGER.
fenestrated triangular lattice wing. Therefore the skeleton becomes very similar to Clathrocorys (PL 64, figs. 8-10), but wants the regular central cephalis.
Dimensions. — Length of the apical spine 0'2, of the basal spines 0'14.
Habitat. — Central Pacific, Station 271, depth 2425 fathoms.
Genus 397. Periplecta,1 Haeckel, 1881, Prodromus, p. 424.
Definition — P lectanida with, four unequal radial spines, arising in pairs from the two poles of a common central rod ; one ascending apical spine opposed to three descending basal spines.
The genus Periplecta has probably been derived from Plagiocarpa (by concrescence of the meeting spine branches), and has the same important relation to a part of the triradial Stephoidea (Cortina, &c.) and Cyrtoidea (Pteroscenium, &c.). It differs from the latter only in the fact that the loose irregular framework connecting the bases of the four cortinar spines is not a regular lattice-shell.
1. Periplecta cortina, n. sp. (PI. 91, fig. 10).
Spines of very different size and shape, three-sided prismatic. The apical spine (or horn) is larger, nearly straight, and bears a verticil of three large divergent branches, which are again ramified. The three basal spines (or feet) are curved, pinnate, each with three to five pairs of opposite simple curved branches. A small common central rod separates the two united pectoral feet from the two other spines (the caudal foot and the apical horn). The three basal feet are connected by three convex bows composing a horizontal collar ring, and since the central rod is prolonged between the pectoral feet to the ring, a very remarkable collar septum is formed with four cortinar meshes. Above this septum an irregular spongy shell, including the central capsule, is formed by a delicate framework, interwoven between the apical horn and the three basal feet.
Dimensions. — Length of the apical spine 0'25 to 0'3, of the three basal spines 0'15 to 0'2.
Habitat. — Central Pacific, Station 271, surface.
2. Periplecta pteroscenium, n. sp.
Spines of very different size and shape, three-sided prismatic, verticillate. The apical spine (or horn) with ten to twelve verticils, is one and a half times as long as the three basal spines (or feet), which bear six to eight verticils only; each verticil with three branches which by communicating ramules form a loose irregular wickerwork. Similar to Pteroscenium pinnatum, PL 53, figs. 14-16, but without a regular lattice-shell. A short basal central rod separates two equal (pectoral) spines from two unequal spines, the larger of the latter is the apical, the shorter the caudal spine.
Dimensions. — Length of the apical spine 0'26, of the three basal spines O'l7.
Habitat. — Central Pacific, Station 274, surface.
1 Periphcta = Surrounded by a hunting net ; «•£{/, •a^tx.Tti.
REPORT ON THE RADIOLARIA. 927
3. Periplecta monocyrtis, n. sp.
Spines of nearly equal size and shape, cylindrical, irregularly branched. The apical spine is straight, more branched and nearly twice as long as the three basal spines. All four spines in the basal third connected by a loose spongy framework, approaching the form of some Monocyrtida.
Dimensions. — Length of the apical spine 0'24, of the basal spines 0'13.
Habitat. — Central Pacific, Station 274, surface.
Subfamily 3. HEXAPLECTIDA, Haeckel. Definition. — P lectanida with six radial spines.
Genus 398. Hexaplecta^ Haeckel, 1881, Prodromus, p. 425.
Definition. — P lectanida with six radial spines, arising from one common central point.
The genus Hexaplecta has probably been derived from Hexaplagia by concrescence of the meeting branches of the six spines, and therefore has to it the same relation that Plectophora bears to Plagiacantha. The two species here described represent perhaps two different genera, since in the first all six spines are equal, opposed in pairs, in the second different in pairs (three upper smaller and three lower larger).
1. Hexaplecta triaxonia, n. sp.
Spines equal, opposite in three crossed pairs, straight, three-sided prismatic, thorny, in the distal half with three leaf-shaped, dentate edges, in the basal half with three verticils of slender branches, which are connected by parallel threads, and so form an arachnoidal network with rect- angular or rhomboidal meshes.
Dimensions. — Length of the spines 0'22, of their basal branches 0'06.
Habitat. — South Pacific, Station 285, depth 2375 fathoms.
2. Hexaplecta tricladonia, n. sp.
Spines unequal, three larger spines (in the lower half of the body) being opposite to three smaller spines (in the upper half). The latter are nearly horizontally expanded, each bearing three straight divergent branches. The larger are stronger, twice as long and armed with three verticils, each of three branches. All six spines are slender, three-sided prismatic. Their branches are very thin, thread-shaped, and form by their union a loose network with irregular polygonal meshes.
Dimensions. — Length of the larger spines 0'25, of the smaller 0'12.
Habitat. — South Pacific, Station 291, surface.
1 Hexaplecta = Hunting net with six beams ; %!•
928 THE VOYAGE OF H.M.S. CHALLENGER.
Genus 399. Plectanium? Haeckel, 1881, Prodromus, p. 424.
Definition. — P 1 e c t a n i d a with six radial spines, arising in two opposite divergent groups from the two poles of a common central rod.
The genus Plectanium has been derived from Plagonium by concrescence of the meeting branches, and bears therefore to it the same relation that the preceding Hexaplecta exhibits to Hexaplagia. Whilst in these two latter genera the six spines arise from a common central point, they arise here in two divergent groups from the two poles of a horizontal common middle rod, similar to the spicula of many Beloidea.
1. Plectanium trigeminum, n. sp. (PL 91, fig- H)-
Spines straight and stout, six to eight times as long as the common middle rod, three-sided prismatic ; in the distal half thickened, with three divergent terminal thorns ; in the basal half with three to four verticils of thin lateral branches, which are again ramified, and by their united threads produce an irregular loose framework.
Dimensions. — Length of the spines 0'25, basal breadth 0'005, terminal breadth 0'02; length of the middle rod 0'03.
Habitat. — North Pacific, Station 244, surface.
2. Plectanium ovodimare, n. sp.
Spines straight and stout, three-sided prismatic, about four times as long as the common middle rod, gradually thinned towards the distal end ; in the basal half with two to three verticils of forked branches, which are dichotomously ramified, and by their united threads form a loose ovate framework.
Dimensions. — Length of the spines 017, of the middle rod 0'04.
Habitat. — North Pacific, Station 236, surface.
3. Plectanium sphcerozoum, n. sp.
Spines straight, cylindrical, ten to twelve times as long as the common middle rod, with six to eight verticils of thorny branches, tapering towards the distal end; the branches of the verticils are simple in the distal half, again ramified in the basal half, and here connected together by irregularly branched threads forming a loose framework. (Resembles one spiculum of SpJuxrozoum verticillatum, PI. 4, fig. 7, but is more richly branched, with united ramules.)
Dimensions. — Length of the spines 0-2, of the middle rod OD1.
Habitat. — Central Pacific, Station 266, surface.
1 Plectanium = Small wickerwork or network ;
REPORT ON THE RADIOLARIA. 929
Subfamily 4. POLYPLECTIDA, Haeckel, 1881, Prodromus, p. 424. Definition. — P lectanida with numerous (seven to nine or more) radial spines.
Genus 400. Polyplecta,1 Haeckel.
Definition. — P lectanida with numerous (seven to nine or more) radial spines, arising from a common centre and lying in different planes.
The genus Polyplecta comprises provisionally all Plectanida possessing seven or more radial spines, united in the centre of the framework. It may be derived from Polyplagia by meeting and concrescence of the free branches. But as in the latter genus, here also the few observed species are very different, perhaps of different origin, and may be afterwards better separated as representatives of diverse genera.
1. Polyplecta heptacantha, n. sp. (PI. 91, fig. 12).
Heptaplegma heptacantha, Haeckel, 1882, MS.
Seven unequal spines divergent from one common central point, slender, slightly curved, three- sided prismatic. Four spines are much larger, twice to three times as long and as thick as the three smaller spines. One of the four larger spines is directed upwards (as " apical horn "), whilst the three others diverge downwards (as " basal feet "). Each of the four larger spines bears five to seven equidistant verticils of three divergent branches, the proximal of which are branched, the distal simple. The three smaller spines lie nearly horizontally, midway between the odd apical spine and the three basal spines, and in the same meridian planes with them ; each bears one verticil of three divergent branches. All the branches are united by arachnoidal threads, composing a loose wickerwork with irregular, generally quadrangular meshes.
Dimensions. — Length of the four larger spines 0'27 to 0'33, of the four smaller O'l to 0'14.
Habitat. — Central Pacific, Station 271, surface.
2. Polyplecta enneacantha, n. sp.
Enneaplegma enneacantha, Haeckel, 1881, Prodromus, p. 425.
Nine equal and equidistant, straight, cylindrical radial spines, lying nearly in one plane, arise from an irregular spongy central framework ; six of them seem to be secondary, intercalated between three equidistant primary spines, which are united in the centre. (This species resembles in the nine-radial structure the remarkable Enneaphormis rotula, PL 57, fig. 9, and may perhaps be derived from a similar species ; but it has no regular latticed shell.)
Dimensions. — Length of the spines 0'22, diameter of the framework O'l1?. .Habitat. — Central Pacific, Station 266, depth 2750 fathoms.
1 Po%)Z«cta = Much entwined ; TroTi^xsxrof.
(ZOOL. CHALL. EXP. — PART XU — 1886.) .Rr 11, 7
930 THE VOYAGE OF H.M.S. CHALLENGER.
3. Polyplecta decacantha, n. sp.
/
Pentaplegma decacantha, Haeckel, Prodromus, p. 425.
Ten radial spines, curved, cylindrical, irregularly branched, diverge in different directions and seem to arise in pairs from an irregular central framework, in the centre of which five primary spines are united ; the latter correspond probably to the five spines of Pentaspyris, &c. The density of the spongy central framework did not allow of an accurate investigation, and makes it doubtful whether this species is not a Spongiomma.
Dimensions. — Length of the spines 0'3 to 0'4, diameter of the framework 0'18.
Habitat. — Tropical Atlantic, Station 338, depth 1990 fathoms.
4. Polyplecta polybrocha, Haeekel.
1 Acanthodesmia polybrocJia, Haeckel, 1865, Zeitschr. f. wiss. Zool., Bd. xv. p. 368, Taf. xxvi.
fig. 3. Plegmosphcera polybrocha, Haeckel, 1881, Prodromus, p. 455.
Numerous (twenty to thirty or more) radial spines, thin, cylindrical, curved and irregularly branched, arising from an irregular central spongy framework, are connected by numerous slender arches. The specimen observed by me in 1880 in Portofino was a true Polyplecta, with three primary spines centrally united, between which numerous other spines were intercalated. The similar specimen, however, observed in 1864 in Villafranca, and figured, loc. cit., was perhaps a Plegmosphcera.
Dimensions. — Length of the radial spines 0'05 to O'l, diameter of the framework 016.
Habitat. — Mediterranean (Villafranca, Portofino), surface.
5. Polyplecta dumetum, Haeckel.
Acanthodesmia dumetum, J. Miiller, 1858, Abhandl. d. k. Akad. d. Wiss. Berlin, p. 30, Taf. i. fig. 3.
Numerous (ten to twelve or more) radial spines, thin and straight, with a few straight lateral branches, diverge in different directions and are connected by a few slender curved arches. Some similar forms, but more developed, with numerous branches and curved rods, are found in the Pacific Eadiolarian ooze, and represent probably different species.
Dimensions. — Length of the radial spines 0'05 to 0'08, of the branches 0'02 to 0'03.
Habitat. — Mediterranean, French shore (Cette and Saint Tropez), Johannes Miiller, surface
REPORT ON THE RADIOLARIA. 931
Suborder III. STEPHOIDEA, Haeckel.
Stephoidea vel Stephida, Haeckel, 1881, Prodromus, p. 444. Acanthodesmida (sensu ampliori), Biitschli, 1882, Zeitschr. f. wiss. Zool., vol. xxxvi. p. 495.
Definition. — NASSELLABIA without complete lattice -shell, with a skeleton composed of one or more simple rings, which may be united by a loose framework and are separated by large openings or gate's. One primary or sagittal ring, determining the sagittal or median plane of the bilateral body, encloses the monaxonian central capsule.
The suborder Stephoidea, hitherto known by a few species only of " Acantho- desmida," comprises a large number of interesting NASSELLARIA (now more than two hundred species), which possess peculiar interest for the morphology and phylogeny of this legion. The monaxonian central capsule of the Stephoidea is surrounded either by one simple ring or by a complex system of several loosely connected rings ; these may be united by a loose framework of connected branches, but never produce a com- plete lattice-shell, as is constantly the case in the Spyroidea, Botryodea, and Cyrtoidea. Therefore there remain between the parts of the connected rings a few large openings which we call "gates," separating them from the numerous small "pores" of the complete lattice-shells. In the most simple case, if only one ring be formed, there is also present only one " gate," the aperture of this simple ring.
The first known species of Stephoidea were observed in the Mediterranean by Johannes Miiller in 1856, and described and figured in his last treatise (1858) under the names Lithocircus annularis (loc. cit., Taf. i. fig. 1) and Acanthodesmia vinculata (loc. cit., Taf. i. figs. 4—7). In the following year I myself observed two other living species in the Mediterranean, and described them in my Monograph (1862, pp. 268, 270) as Zygostephanus miilleri (Taf. xii. fig. 2) and Prismatium tripleurum (Taf. iv. fig. 6). For these four longest known Stephoidea I founded the new family of Acanthodesmida (loc. cit., p. 265), but united with them two other similar genera which I afterwards separated : — Plagiacantha (belonging to the Plectoidea) and Dictyocha (belonging to the PH^EODAKIA).
When, in 1876, I received the rich material of the Challenger collection, I was astonished to find in it an enormous number of new, similar, and partly very interest- ing "Acanthodesmida," which were afterwards arranged in my Prodromus (1881, p. 444) in thirty-eight different genera and four " subfamilies," all united in one single large family, " Stephida or Monopylaria cricoidea." I retain here this natural group in the same sense, but give to it the rank of a " suborder," separating at the same time its four subfamilies as substantial " families." Since the names of the
932 THE VOYAGE OF H.M.S. CHALLENGER.
latter, proposed in the Prodromus, were not quite suitable, I replace them here by the following more convenient names : —
1. Family Stephanida ( = Monostephida, 1881, p. 447). Skeleton entirely formed
by one simple ring (the primary vertical sagittal ring). The only " gate " is the simple aperture of the ring.
2. Family Semantida ( = Dyostephida, 1881, p. 446). Skeleton composed of
two rings, perpendicular to one another ; the primary vertical sagittal ring bears at the base a horizontal basal ring ; between the two rings two or more " basal gates remain."
3. Family Coronida ( = Triostephida, 1881, p. 445). Skeleton composed of two
crossed vertical or meridional rings, perpendicular to one another — the primary sagittal ring and the secondary frontal ring. Commonly the two vertical rings are united at the base by a horizontal basal ring, and between them remain two or more " basal gates."
4. Family Tympanida ( = Parastephida, 1881, p. 446). Skeleton composed of
two parallel horizontal rings, an upper mitral ring, and a lower basal ring, both connected by vertical or divergent columellae, which are parts of vertical rings (primary sagittal, and secondary frontal ring).
The peculiar structure of the central capsule of the Stephoidea, and their character as true MONOPYLEA, were first recognised by Eichard Hertwig, who in 1879, in his Organismus der Eadiolarien, gave an excellent detailed description of it (loc. cit., pp. 68—72, Taf. vii. figs. 4, 5). He also pointed out the near affinity of these " Acanthodesmida " with the Spyroidea or Zygocyrtida, uniting the latter with the former family.
A fuller explanation of this affinity, and of the great morphological and phylo- genetic importance of the " Acanthodesmida," as ancestral forms of the Spyroidea and Cyrtoidea, was given in 1882 by Butschli (Zeitschr. f. wiss. Zool., vol. xxxvi. pp. 495—501). He described in detail some important fossil forms of Acanthodesmida as different species of " Stephanolithis," a name which Ehrenberg had employed for various ring-like fragments of Eadiolarian shells, sponges, and other fossil bodies. The four fossil species which Butschli described represent four different genera of Stephoidea, viz., Semantis (spinescens), Semantrum (mulleri], Semantidium (haeckelii), and Tristephanium (hertivigii). On the phylogenetic conclusions, derived from these accurate observations, compare above, p. 893, &c. The topographical signifi- cation of the parts, employed by Butschli, is contrary to mine ; he calls my dorsal side the " anterior," and my ventral side the " posterior."
The geometrical fundamental form of the body in nearly all Stephoidea (with few exceptions) is distinctly bilateral or " dipleuric," so that we can easily distinguish the
REPORT ON THE RADIOLARIA. 933
three different dimensive axes : the principal axis with different apical aad basal poles, the sagittal axis with different dorsal and ventral poles, and the lateral axis with equivalent right and left poles. In only a few genera this bilateral symmetry is not expressed, and a simpler, more regular fundamental form appears. The latter may be either primary (in the monaxonian Archicircus and Lithocircus) or secondary, afterwards acquired (in the octahedral Trissocircus and Trissocydus, the cubical Lithocubus, the prismatic Eutympanium, and some other forms).
The most important element of the skeleton, with which its formation begins, in all Stephoidea is the simple primary or sagittal ring, lying vertically in the sagittal or median plane of the body and surrounding the monaxonian central capsule. This sagittal ring is the only essential element of the skeleton in all Stephanida, and is completely preserved in all Semantida, also in the greater part of the Coronida and Tympanida. It is partially reduced in the small groups of the true Acanthodesmida (subfamily of Coronida) and the Dystympanida and Eutympanida (subfamilies of Tympanida). Here only the vertical parts of it are preserved (dorsal and ventral rod), whilst the horizontal parts are lost (mitral and basal rod).
The sagittal ring, lies constantly in the vertical median plane of the body, and. therefore divides the enclosed central capsule into a right and a left half. It is rarely regular or subregular, commonly dipleuric or distinctly bilateral, so that we may easily distinguish its dorsal and ventral, apical and basal parts. The most important of these four parts or " rods " is the " basal rod " or the inferior part, because here the ring is in closer connection with the central capsule and its "porous area"; here peculiar spines or branches are commonly developed, which even on the isolated ring immediately determine the basal pole. The opposite upper part, or the " mitral rod," is also often distinguished by peculiar appendages. The posterior part, or the " dorsal rod " (the anterior rod, a, in the description of Biitschli), is commonly more straight, often quite vertical. The opposite anterior part, or the " ventral rod " (the posterior rod, &, of Biitschli), is usually more convex, and often strongly curved or semicircular,
AVhilst this dipleuric or bilateral (commonly obliquely ovate or nearly triangular) form of the sagittal ring is distinctly preserved in by far the greater number of Stephoidea, it is replaced in some few genera by a more regular, amphitheet, diphragmatic, or biradial form. In this case we may often suppose a primary regularity to exist, the dorsal and ventral parts being not yet differentiated, as in Archicircus and Lithocircus, Zygo- stephanus and Protympanium, and perhaps also in some other forms. But in other cases the regularity is, on the contrary, secondary, being derived from original bilateral forms.
The rod of the sagittal ring is either cylindrical (with circular transverse section) or angular (commonly with triangular transverse section). In nearly all Stephoidea (with very few exceptions) branches or apophyses are developed from the ring, regular^ disposed and often of very great morphological importance. Commonly "these
934 THE VOYAGE OF H.M.S. CHALLENGER.
apophyses are developed in pairs, growing symmetrically on both sides of the ring. The most important of these apophyses are : — (l) basal apophyses, arising from the basal pole of the ring ; (2) mitral apophyses, arising from the apical pole ; (3) dorsal apophyses, arising from the middle of the dorsal rod ; and (4) ventral apophyses, arising from the middle of the ventral rod. The two former arise in the principal axis, the two latter in the sagittal axis of the body. Very frequently the latter pair is replaced by two pairs of transverse branches, one inferior (mandibular) and one superior (orbital). The apophyses of the ring are either simple or branched, often very large, richly ramified, and give origin to a number of further products.
Whilst in the Stephanida the primary sagittal ring alone represents the whole skeleton, it produces in all other Stephoidea one or more secondary rings. The most important of these is the horizontal basal ring, appearing first in the Semantida (PL 92). From the base of the sagittal ring there arise in the horizontal basal plane two pairs of lateral branches or " basal apophyses." The curved opposite branches of the corresponding pairs become united on each side of the primary ring (right and left), and so produce a second, horizontal ring, perpendicular to the former. This basal ring encloses two paired basal gates, which are enclosed on the medial side by the basal rod of the sagittal ring, and on the lateral side by two united apophyses (Semantis, PI. 92, figs. 1, 2). These two primary basal gates are of the greatest morphological importance; we call them the "jugular gates or jugular pores " (in the description of Biitschli, the pores I, loc, cit., p. 498). The dorsal pair of basal apophyses (on their posterior edge) are the coracal rods, e (rods e of Biitschli) ; the opposite ventral pair (on their anterior edge) are the clavicular or furcular rods, f (rods el of Biitschli); compare Pis. 92-95, and their explanation.
The skeleton of Semantis, the prototype of the Semantida, thus assumes the characteristic form of a signet-ring. The basal ring enclosing the two jugular pores corresponds to the seal-plate. It is commonly more or less horizontal ; but often the apophyses descend obliquely (PL 92, figs. 1, 2, 13, &c.), more rarely laterally (PL 29, fig. 11). The further development of this typical form is essentially effected by the production of new basal pores in the horizontal seal-plate. In Semantrum (PL 92, figs. 3, 4, 5) we find already four basal gates. Behind the jugular gates is formed a second pair, the " cardinal gates " (pores II of Biitschli). These are enclosed on the anterior margin by the coracal rods (e), on the posterior margin by the scapular rods (d), a third pair of basal apophyses, arising behind the former from the sagittal ring and uniting with them (the rods e2 of Biitschli). Commonly the two posterior, or cardinal gates are much larger than the two anterior, jugular gates. This characteristic basal plate of Semantrum, with two pairs of basal pores, is of the greatest morphological importance, as it is inherited in by far the greater number of the NASSELLAEIA, though not so generally as Biitschli supposes. The basal ring of Semantrum is either more circular
REPORT ON THE RADIOLARIA. 935
or elliptical, or more polygonal, and is connected with the basal rod of the sagittal ring by three pairs of radial apophyses, the anterior furcular, the middle coracal, and the •posterior scapular rods.
A third important form of Semantida is Semantidium (PL 92, figs. 6, 7). Here we find three pairs of basal pores in the seal-plate ; the third pair, newly formed, consists of the cervical gates (e), bounded in front by the scapular rods (cZ), behind by a fourth pair of basal apophyses, the cervical rods.
The basal apophyses of the sagittal ring are not only of great morphological importance, because they produce by their union three typical pairs of basal gates or " collar pores," but also because their prolongations often appear as typical basal feet. The distal prolongations of the coracal rods appear in Semantiscu-s (PL 92, figs. 16—18) as two pectoral feet, those of the scapular rods as two tergal feet, whilst the opposite prolongations of the basal rod of the sagittal ring appear as two " sagittal feet " (in front an anterior or sternal, and behind a posterior or caudal foot). In the typical Cortiniscus (PL 92, figs. 11—13) only three feet are developed; an odd caudal and two paired pectoral feet (compare above, p. 891). The typical basal ring of the Semantida, with its paired basal gates (Semantis), reappears in the majority of the Coronida, differing from the former in the development of a second vertical ring, which lies in the frontal plane (perpendicular to the sagittal ring), and which we therefore call the frontal ring. In only one small group of the Coronida the basal ring is absent, namely, in the Zygostephanida, and here the frontal ring appears in the simplest form, as a complete elliptical meridian ring, crossing the sagittal ring perpendicularly on the -two poles of the main axis (Zygostephanus, PL 93, figs. 1—4). Four large lateral gates between the two rings remain open. This form may be derived directly from the Stephanida in the following way ; from both poles of a simple sagittal ring there arise two opposite lateral apophyses, which in the frontal plane become curved one towards the other, and united in the poles of the transverse axis. The basal apophyses would be the coracal rods. But it is also possible that Zygostephanus was derived from Semantis by the loss of the furcular rods.
The three typical rings (or the " dimensive rings ") of the Stephoidea appear in their most complete form in the subfamily Trissocyclida (PL 93, figs. 7, 13). Here all three rings are undivided and completely developed in the three dimensive planes, perpendicular one to another. Between them there remain eight large open gates ; the four superior are the four " lateral gates " of Zygostephanus, the four inferior are the four basal gates of Semantrum. The four latter are originally much smaller than the four former; but in Trissocircus and Trissocyclus (PL 93, figs. 10—12) they reach the same size. Therefore all eight gates are here of equal form and similar size, and the basal ring, now a true equatorial ring, divides the two meridional rings into two equal halves.
In the Eucoronida, a third subfamily of Coronida, the sagittal and the basal rings
936 THE VOYAGE OF H.M.S. CHALLENGER.
are complete, but the frontal ring is incomplete, its basal part being wanting (PL 82, figs. 4—6). Therefore we find here six large gates between the three rings; four upper lateral gates (between the two crossed vertical rings) and two lower basal gates (between the basal rod of the sagittal ring and the two halves of the basal ring). Eucoronis, the type of this subfamily, may be derived either directly from Semantis by development of a frontal ring, or from Tristephanium by loss of the basal part of the frontal ring.
A quite simple basal ring, with a single gate, distinguishes the fourth subfamily of Coronida, the Acanthodesmida (sensu restricto), the genera Coronidium (PI. 82, figs. 1, 2, 7, 8) and Acanthodesmia (PL 93, fig. 5). The horizontal basal ring alone is here complete, whilst both vertical rings (the sagittal and frontal rings) are incomplete, their basal parts being wanting. Therefore there are here five gates, four lateral and one basal. These forms may be derived from Eucoronis by loss of the basal rod of the primary sagittal ring.
The Tympanida, the fourth family of S t e p h o id e a, exhibit another type of ring structure. Here two parallel horizontal rings are constantly developed, one on the apical pole, the other on the basal pole of the sagittal ring. The latter is the same basal ring as in the Semantida and Coronida. The former is a " mitral ring," developed in the same manner, by union of two pairs of horizontal lateral branches, which arise on both sides from the apical rod (or mitral rod) of the sagittal ring. In the simplest case these two parallel horizontal rings are connected only by the sagittal ring, which is either complete (Protympanium, PL 93, fig. 14) or incomplete (Parastephanus, PL 93, fig. 21). But commonly also an incomplete frontal ring is present, so that the two horizontal rings are connected by four vertical or sub vertical rods ; two of these " columellse " are the dorsal and ventral rods of the sagittal ring, the two others are the lateral rods of the frontal ring. Between the former and the latter are sometimes developed two, four, or more accessory columellse (probably halves of accessory incomplete diagonal meridian rings). In this way arise the characteristic " drum -forms " of many Tympanida, in which the two parallel horizontal rings correspond to the upper .and lower rings of a drum, whilst the connecting vertical columellse correspond to its parallel lateral rods (PL 83, figs. 1, 2, &c.).
Originally the two horizontal rings of these " drum-shells " are both bisected by the complete sagittal ring, each provided with two lateral gates (Protympanida). But in the Eutympanida both rings exhibit one simple gate only, the apical and the basal rod of the sagittal ring being lost. In the Paratympanida both rings are closed by a secondary lattice -plate, whilst in the Dystympanida the upper (mitral) ring alone is closed by such a plate, the lower (basal) ring is open. In some Eutympanida the shell assumes the .strange form of a regular geometrical cube, the twelve edges of which are represented by thin rods of silex (Liihocubus) — its four upper edges represent the mitral ring, the four lower the basal ring ; two opposite of the four vertical cube-
REPORT ON THE RADIOLARIA. 937
edges are the lateral halves of the frontal ring, the two other alternate ones are the remaining halves of the reduced sagittal ring (dorsal and ventral rod) (PI. 82, fig. 12).
In many Tympanida and Coronida a loose irregular lattice or framework is developed, which partly closes the large open gates. But this never reaches the com- pleteness of a true lattice -shell, such as we find in the Spyroidea, Botryodea, and C y r t o i d e a. In by far the greater number of Stephoidea the corners, and partly also the rods, of the shell are armed with numerous irregular spines, often forked or richly branched. Among these spines the descending " basal apophyses " possess a peculiar importance, since by their regular number and disposition they correspond to the radial rods of the Plectoidea, and to the typical " feet " of the Spyroidea and Cyrtoidea. The most important of them are the three cortinar feet (one caudal and two pectoral) of Cortina, Cortiniscus, &c. (compare above, p. 891).
The Central Capsule exhibits in the Stephoidea the same characteristic structure as in all other MONOPYLEA, first exactly pointed out by Richard Hertwig in 1879 (Organismus der Radiol., p. 71, Taf. vii. figs. 4, 5). Its form is commonly ovate or ellipsoidal, sometimes also lentelliptical or nearly spherical. It exhibits constantly on the basal pole the porochora or porous area, and in the basal half the podoconus or pseudopodial cone. From the surrounding sagittal ring it is separated by a thick jelly-like calymma, which commonly exhibits numerous zooxanthellae. The numerous pseudopodia are commonly branched, with rather rare anastomoses. The membrane of the central capsule is thick.
Synopsis of the Families of Stephoidea.
I. Skeleton composed of the simple vertical sagittal ring only, without secondary
rings, . . . . . . . . .1. STEPHANIDA.
II. Skeleton composed of two crossed rings, a vertical sagittal and a horizontal basal
ring, ......... 2. SEMANTIDA.
III. Skeleton composed of two crossed vertical meridional rings (a primary sagittal
and a secondary frontal ring), commonly also with a horizontal basal ring, . 3. CORONIDA.
IV. Skeleton composed of two parallel horizontal rings (upper mitral and lower basal
ring), both connected by a vertical sagittal ring (and often by a vertical frontal
ring), . . . . . . . . .4. TYMPANIDA.
Family XLVIII. STEPHANIE A, Haeckel (PI. 81).
Monostephida, Haeckel, 1881, Prodromus, p. 447.
Definition. — S tephoidea with a simple sagittal ring, without any lattice -work.
The family Stephanidais the most simple of all Stephoidea, and probably the common ancestral group of this suborder (compare above, p. 933). The skeleton
(ZOOL. CHALL. EXP. PART XL. 1886.) Rr 118
938 THE VOYAGE OF H.M.S. CHALLENGER.
consists of a simple ring only, surrounding the central capsule, and armed commonly with simple thorns or with larger branched spines. The branches of these spines are constantly free, never joining together. Therefore the shell exhibits no trace of fenestration or lattice-work, no pores or gates, except the simple large gate of the ring itself. In all other Stephoidea we find secondary gates or lattice-work.
The first known form of this family is Lithocircus annularis, described by Johannes Miiller in 1858 (Abhandl. d. k. Akad. d. Wiss. Berlin, p. 29, Taf. i. fig. 1). He observed already the central capsule (" Blase ") surrounded by the circular ring of silex, and the calymma (" Strahlige Gallert ") enveloping the whole body. The peculiar structure of the soft body, particularly the " area porosa " on the basal pole of the central capsule, and the pseudopodial cone within it, were first accurately described by Hertwig (in 1879). A great number of simple rings, similar to these, were found in the Challenger collection, and are here arranged in six genera and forty-eight species.
The simple ring of silex, which alone forms the skeleton of the Stephanida, corresponds to the primary or sagittal ring of the other Stephoidea, and lies there- fore vertically in the median or sagittal plane of the body. We can therefore distinguish on it four different segments, rods or bows, two of which are more horizontal, two more vertical. The former are one upper bow or apical rod, and one lower bow or basal rod. The latter are one posterior bow or dorsal rod, and one anterior bow or ventral rod. Sometimes each of these four component bows is distinguished by a corner-spine, or by a pair of divergent branches.
In the two simplest (and probably oldest) genera of Stephanida, in Archicircus and Lithocircus, the dorsal and ventral rods of the ring are equal and cannot be distinguished ; therefore the fundamental form is here amphithect, diphragmatic, or biradial (the poles of the sagittal axis being equal). In the four other genera the dorsal rod is more straight (often vertical) and more or less different from the ventral, convexly curved rod ; therefore the fundamental form is here dipleuric or bilateral, as in the greater number of all NASSELLARIA (the poles of the sagittal axis being unequal). The general form of the ring in this latter case is commonly obliquely ovate or nearly triangular, the basal pole being more pointed, the apical pole more* rounded (PI. 81).
The rods or bows of the ring are either roundish or cylindrical (with circular or elliptical transverse section), or they are prismatic or angular (commonly with triangular transverse section). In the latter case one edge usually is prominent in the sagittal plane (on the convex outside of the ring), whilst two other edges diverge laterally on both sides of it. The inner or concave margin of the ring is commonly smooth.
The inner perimeter of the large gate, enclosed by the ring, is commonly rounded (elliptical or ovate), rarely angular. However, the outer perimeter of the ring is
REPORT ON THE RADIOLARIA. 939
nearly always polygonal, with prominent corners, and usually from these arise thorns or branched spines which are regularly disposed. Regarding this disposition we may distinguish three cases : A, the spines lie in the sagittal plane and form a single row, arising from the median edge ; B, the spines lie on both sides of the latter and form two parallel rows, arising from the two lateral edges ; C, the spines represent a com- bination of A and B, and are disposed in three rows, two paired rows arising from the two lateral edges, and an odd middle row between them, arising from the median edge. The spines are simple, without branches, in Archicircus and Zygocircus ; more or less branched in Lithocircus and Dendrocircus. The branches are often richly ramified or arborescent, and exhibit great variety in size, special form, and direction (compare PL 81).
The number and disposition of the spines or groups of spines are usually constant, and may be employed in the further progress of our knowledge, to distinguish a number of genera and subgenera. Very commonly (perhaps in the majority of the Stephanida) we find six groups of spines, an apical group on the upper rod of the sagittal ring, a basal group on the lower rod (on the porochora of the central capsule), two ventral groups on the anterior rod, and two dorsal groups on the posterior rod. In other species we find four or eight groups instead of six, and sometimes a larger number.
The most important of these apophyses of the ring are the basal spines, arising from its basal pole, where the porochora of the central capsule rests upon it. They are often much larger and more branched than the other spines, and attain a peculiar morphological value in the small subfamily Cortinida. Here we .find three or four regularly disposed " basal spines," which may be compared to the typical " basal feet " of the Cyrtellaria, appearing in the majority of Spyroidea and Cyrtoidea. Cortina, one of the most important NASSELLARIA, bears three typical divergent feet on the base of the simple ring, two paired anterior or " pectoral feet," and an odd posterior or " caudal foot." The latter appears as a direct basal prolonga- tion of the dorsal rod of the ring, and is opposed to an upper prolongation of the same, which corresponds to the "apical horn" of the Cyrtellaria (PI. 97, figs. 1—3). As already explained above, these three basal feet of Cortina possess the highest phylo- genetic value, since they may also be compared with the three primary radial spines of the Plectoidea, and so connect the Cyrtellaria and the Fleet ella.ria. Steplianium differs from Cortina in the possession of four basal feet, an odd anterior or " sternal foot " being added to the three typical feet of the latter (PI. 92, figs. 20, 21). Some forms of Plectoidea (Plagoniscus, Plectaniscus, &c.) seem to be nearly related to these Cortinida, and may be easily transformed into them by development of a complete ring, embracing the central capsule. They seem to demonstrate the near affinity of all these triradiate NASSELLAKIA (PI. 91, figs. 4, 5, 9, 10).
940
THE VOYAGE OF H.M.S. CHALLENGES.
I. Subfamily
Lithocircida.
No typical basal feet on the base of the ring (no cortinar feet).
II. Subfamily
Cortinida.
Three or four typical basal feet on the ring (cortinar feet).
Synopsis of the Genera of Stephanida.
{Ring smooth or thorny, with- out branched spines. Ring armed with branched
(
spines,
I" Ring smooth or thorny, with-
Ring dipleuric, bilateral ; j out branched spines, dorsal and ventral bow -j different Ring armed with branched
[ spines.
Three basal feet (and an ( apical horn). |
One caudal and two lateral feet,
Four basal feet (and an / Two sagittal and two lateral apical horn). ( feet,
401.
402.
403.
404.
405.
406.
Arcliicircus.
Lithocircus.
Zygocircus.
Dendrocircus.
Cortina.
Stephanium.
Subfamily 1. LITHOCIRCIDA, Haeckel. Definition. — S tephanida without typical basal feet or cortinar feet.
Genus 401. Archicircus,1 n. gen.
Definition. — S tephanida with a simple amphithect or diphragmatic ring, smooth or thorny, without branched spines and basal feet.
The genus Archicircus is the most primitive and simplest form of all Stephoidea, and probably the common ancestral form, not only of this suborder, but of the greater number of all NASSELLARIA (compare above, p. 893). The skeleton consists only of a quite simple sagittal ring, in which commonly a slight difference of both poles of the main axis (basal and apical pole) is visible, but no difference between the dorsal and the ventral bow of the ring. In my Prodromus (1881, p. 447) the species of Archicircus were disposed partly in the subgenus Monostephus, partly in the genus Lithocircus.
Subgenus 1. Monostephus, Haeckel, 1881, Prodromus, p. 447. Definition. — Ring circular, elliptical, or ovate, without prominent corners.
1 . Archicircus princeps, n. sp.
Gate circular. King circular, smooth, its transverse section also circular. The simplest form of all Stephoidea.
Dimensions. — Diameter of the gate 0'05 to 0-08 ; thickness of the ring O'OOG to O'OOS. Habitat. — Central Pacific, Stations 265 to 274, depth 2350 to 2925 fathoms.
1 Archicircus = Primordial ring; ajjc'i *'j*of.
REPORT ON THE RADIOLARIA. 941
2. Archicircus monostephus, n. sp. (PI. 83, fig. 17).
Gate circular. Ring circular, with three elegantly denticulate edges (one outer median and two lateral edges). Transverse section of the ring triangular.
Dimensions. — ^Diameter of the gate 0'06 to 0'08 ; thickness of the ring O'Ol to O'OOS. Habitat. — Central Pacific, Station 274, depth 2750 fathoms.
3. Archicircus ellipsis, n. sp.
Gate elliptical. Eing elliptical, on the inner margin smooth, on the outer margin with fifteen to twenty equal, short, simple, or slightly forked thorns. Transverse section ovate.
Dimensions. — Diameter of the gate 0'05 to 009; thickness of the ring O'Ol to 0'014 Habitat. — Western Tropical Pacific, Station 225, depth 4475 fathoms ; also fossil in Barbados.
4. Archicircus ovalis, n. sp.
Gate ovate. Ring elliptical, smooth, with three prominent, slightly distorted edges, without thorns ; in the transverse section triangular.
Dimensions. — Diameter of the gate 0'08 to 012 ; thickness of the ring 0'006 to 0'009. Habitat. — Tropical Atlantic, Station 347, depth 2250 fathoms.
5. Archicircus monopylus, n. sp.
Gate ovate. Eing ovate, thorny, with three distorted edges, in the transverse section triangular ; surface covered with numerous simple small thorns arising from the three edges.
Dimensions. — Diameter of the gate 01 to 015 ; thickness of the ring O'Ol to 0'012. Habitat. — Indian Ocean (Madagascar), Eabbe, surface.
Subgenus 2. Archistephus, HaeckeL
Definition. — Ring polygonal, with four to six or more prominent corners (and commonly with simple spines arising from the corners).
6. Archicircus quadratus, n. sp.
Gate square. Eing square, with three edges and four short simple pyramidal spines on the four corners, opposite in pairs in two perpendicular diameters. Transverse section triangular. Dimensions. — Diameter of the gate 0'08 ; thickness of the ring O'OOS. Habitat. — Central Pacific, Station 265, depth 2900 fathoms.
942 THE VOYAGE OF H.M.S. CHALLENGER.
7. Archicircus rhombus, n. sp. (PL 81, fig. 7).
Gate rhombic. Eing rhombic, with four prominent edges and four pairs of short, divergent, pyramidal spines on the four corners, arising from the lateral edges of the four rods, about as long as the radius of the gate.
Dimensions. — Diameter of the gate 0'04 to 0'08; thickness of the ring 0'007 to O'Ol.
Habitat. — North Pacific, Station 244, depth 2900 fathoms.
8. Archicircu^ duodenus, n. sp.
Gate square or rhombic. Eing rhombic, with three prominent edges and twelve stout and straight pyramidal spines, about as long as the radius of the gate. In each of the four corners are three divergent spines, arising from the three edges of each two meeting rods.
Dimensions. — Diameter of the gate 0'08 ; thickness of the ring 0'012.
Habitat. — North Atlantic, surface (Rabbe).
9. Archicircus primordialis, n. sp. (PI. 81, fig. 1).
Gate ovate. Eing hexagonal, with three prominent edges and six short pyramidal thorns at the six corners ; the basal thorn is either simple or forked.
Dimensions. — Diameter of the gate 0'07 ; thickness of the ring O'Ol to 0'015. Habitat. — Central Pacific, Stations 265 to 274, depth 2350 to 2925 fathoms.
10. Archicircus hexacanthus, n. sp. (PL 81, fig. 4).
Gate subregular, hexagonal Eing hexagonal, with three sharp edges and six equal radial pyramidal spines, arising from the six corners and placed in the plane of the ring, about as long as the diameter of the gate.
Dimensions. — Diameter of the gate 0'05 to 0'07 ; thickness of the ring O'Ol.
Habitat. — South Pacific, Station 295, depth 1500 fathoms.
11. Archicircus hertivigii, Haeckel.
Lithotircus annularis, R. Hertwig (non J. Miiller), 1879, Organismus der Radiol., p. 69. Taf. vii. fig. 5.
Gate hexagonal, with prolonged main axis. Eing hexagonal, with two prominent edges and six pairs of equal, short, conical spines, arising from the two edges of the six rods at the six corners and divergent on each side of the plane of the ring. The basal spine-pair is doubled, therefore there are in all fourteen spines.
Dimensions. — Diameter of the gate 0'05 to 0'07 ; thickness of the ring O'OOo to O'OOG.
Habitat. — Mediterranean (Messina), Hertwig, surface.
REPORT ON THE RADIOLARIA. 943
12. Archicircus triglyphus, n. sp.
Gate ovate. Ring hexagonal, with three prominent edges and twenty-two to twenty-four simple curved spines, arising from the six corners and about as long as the diameter of the gate. In the basal corner arise six to nine larger spines, protecting the basal pole of the central capsule. From each of the five other corners arise three spines, diverging from the three edges.
Dimensions. — Diameter of the gate 0'07 to Oil ; thickness of the ring O'OOS to O'Oll.
Habitat. — Central Pacific, Station 268, depth 2900 fathoms.
13. Archicircus sexangularis, n. sp. (PL 81, fig. 12).
Gate hexagonal or subcircular. Ring hexagonal, with two sharp prominent edges and six pairs of divergent spines, about as long as the radius of the gate, and arising from the two edges at the six corners. The two apical and the two basal spines are simple and conical, whilst the eight other spines, arising in pairs from the two dorsal and the two ventral corners, are slightly forked.
Dimensions. — Diameter of the gate 0'06 to 0'08 ; thickness of the ring O'Ol to 0'015.
Habitat. — South Atlantic, Station 332, depth 2200 fathoms.
Genus 402. Lithocircus,1 J. Muller, 1856, Monatsber. d. k. preuss. Akad. d. Wiss. Berlin, p.. 484.
Definition. — S tephanida with a simple amphithect or diphragmatic ring, armed with branched spines, without typical basal feet.
The genus Lithocircus is the oldest known form of all S tephoidea, founded by J. Miiller in 1856 for his Lithocircus annularis, the first species of this suborder described. We retain here this cosmopolitan form as the typical representative of the genus, which differs from the preceding Archicircus, its ancestral form, in the develop- ment of branched radial spines.
1. Lithocircus annularis, J. Miiller.
Lithocircus annularis, J. Miiller, 1858, Abhandl. d. k. Akad. d. Wiss. Berlin, p. 29, Taf. i. fig. 1.
Gate circular. Ring circular, with four forked or simply branched spines, opposite in pairs in two diameters, perpendicular one to the other. Spines with slender curved fork-branches, about as long as the diameter of the gate. The specimen figured by J. Miiller bears a supernumerary fifth spine ; numerous other specimens observed by me exhibited a regular cross of four spines.
Dimensions. — Diameter of the gate 01 to 015; length of the spines O'Ol to 018.
Habitat. — Cosmopolitan ; Mediterranean, Atlantic, Indian, Pacific, surface.
1 Lithocircus = Ring of silex ; x/do?,
944 THE VOYAGE OF H.M.S. CHALLENGER.
2. Lithocircus quadricornis, n. sp. (PI. 81, fig. 9).
Gate square. Eing square, with three sharp denticulate edges, and four large bunches of richly branched spines on the four corners. In each corner arise three curved spines, about as long as the diameter of the ring ; their numerous irregular branches are forked and curved like the antlers of deer.
Dimensions. — Diameter of the gate 0'07 ; length of the horns 0'06 to 0'09.
Habitat. — South Pacific, Station 300, depth 1375 fathoms.
3. Lithocircus decimalis, n. sp. (PL 81, fig. 15).
Gate elliptical. Eing pentagonal, with three prominent edges and five pairs of branched spines on the five corners. In each corner arise two or three curved spines, about as long as the radius of the gate, each with two to four forked branches.
Dimensions. — Diameter of the gate 0'08 ; length of the spines 0'03 to 0'05.
Habitat. — North Atlantic, Station 354, surface.
4. Lithocircus hexdblastus, n. sp. (PL 81, fig. 17).
Gate elliptical. Eing hexagonal, with three prominent edges and six pairs of branched spines, arising from the six corners. Each of the twelve spines is short and stout, only half as long as the radius of the gate, and bears a bunch of ten to twenty short, densely aggregated, conical or horn-like curved branches.
Dimensions. — Diameter of the gate 01 ; length of the spines 0'02 to 0'03.
Habitat, — Central Pacific, Stations 265 to. 268, depth 2700 to 2900 fathoms.
5. Lithocircus cratnbessa, n. sp. (PL 81, fig. 6).
Gate elliptical or subcircular. Eing hexagonal, with three wing-shaped distorted edges and six groups of branched spines, arising from the six corners. In each corner arise three short and stout divergent spines, each bearing a bunch of numerous short roundish branches like a cauliflower, scarcely as long as the thickness of the ring.
Dimensions. — Diameter of the ring 01 to 012, length of the spines O'Ol to 0'02.
.Habitat. — Western Tropical Pacific, Station 225, depth 4475 fathoms.
6. Lithocircus tarandus, n. sp. (PL 92, fig. 19).
Gate circular. Eing hexagonal, with three sharp edges and six pairs of large branched spines, arising from the flat lateral edges on the six corners. Each of the twelve spines is horizontally expanded, longer than the diameter of the ring and dichtomously forked like the antlers of a rein-
REPORT ON THE RADIOLARIA. 945
deer. If the lateral ends of the branches of this species become united in the frontal plane, we get Microciibiis, the four upper spines forming the mitral ring, the four middle the equatorial ring, and the four lower the basal ring.
Dimensions. — Diameter of the gate O08 ; length of the spines 0'09.
Habitat. — Central Pacific, Station 272, surface.
7. Lithocircus furcatus, n. sp.
Gate ovate. King ovate, with three sharp prominent edges. The two lateral edges are smooth, The median edge (in the sagittal plane) bears sixteen to twenty forked spines (commonly eight dorsal, eight ventral, and four basal). All the spines are of nearly equal size, slightly curved, and about half as long as the short sagittal axis of the ring.
Dimensions. — Diameter of the gate 0'08 to 012 ; length of the spines 0'03 to 0'04
Habitat. — North Pacific, Station 253, depth 3125 fathoms.
8. Lithocircus magnificus, n. sp. (PI. 81, fig. 16).
Gate ovate or nearly elliptical. King ovate, with three prominent edges, and numerous richly branched spines arising from the three edges. The specimen figured, which I observed living in the Mediterranean, exhibited eight bunches of larger spines, three dorsal, three ventral, one apical, and one basal bunch ; the latter much larger than the seven others. Each bunch was composed of two to four larger and numerous smaller spines, their branches curved and forked. The ovate purple central capsule, with a distinct podoconus, filled more than the half of the gate.
Dimensions. — Diameter of the gate 01 to 013 ; length of the spines 0'05 to 015.
Habitat. — Mediterranean (Portofino, 1880), Atlantic (Canary Islands), Station 354, surface.
Genus 403. Zygocircus,1 Biitschli, 1882, Zeitschr. f. wiss. Zool.,, vol. xxxvi. p. 496,
Definition. — Stephanida with a simple dipleuric or bilateral ring, smooth or thorny, without branched spines and basal feet.
The genus Zygocircus and the following Dendrocircus differ from the two preceding older genera in the bilaterally symmetrical or dipleuric form of the sagittal ring. Whilst in Archicircus and Lithocircus the two sagittal halves or bows of the ring, the dorsal and ventral bow, are equal (therefore the fundamental form amphithect or diphrag- matic), here both bows become distinctly different ; the dorsal bow is constantly more straight (often vertical), the ventral bow more convex (obliquely ascending). This dipleuric differentiation is most important, as it is transmitted to the greater number of NASSELLABIA by heredity.
1 ZygocirciiA = Yoked or symmetrical ring ; £vyti>, x/jxoj. (ZOOL. CHALL. EXP. — PAST XL. — 1886.) Rr 119
946 THE VOYAGE OF H.M.S. CHALLENGER.
1. Zygocircus sagittalis, n. sp.
Gate ovate. Ring half ovate or nearly triangular, with three curved edges and three prominent corners, one apical and two basal protuberances. Dorsal rod vertical, twice as long as the horizontal basal rod. Ventral rod convexly curved.
Dimensions. — Diameter of the gate 0'05 to O07 ; height of the tubercles O01 to 0'015.
Habitat. — Central Pacific, Stations 265 to 268, depth 2900 fathoms.
2. Zygocircus trigonus, n. sp.
Gate triangular. King triangular, with three curved edges and three prominent corners, which are prolonged into nine divergent conical spines ; three spines arising from the three edges of each: corner. Dorsal rod vertical ; ventral and basal rods curved and convergent.
Dimensions. — Diameter of the gate Oil to 013 ; length of the spines O'Ol to 0'015.
Habitat. — Indian Ocean, Sunda Archipelago (Eabbe), surface.
3. Zygocircus tetragonus, n. sp.
Gate ovate. King quadrangular, without edges, with four simple conical spines of different sizes ; one smaller apical, one larger basal, and two equatorial spines of middle size (one dorsal and one ventral). Dorsal and ventral rod curved.
Dimensions. — Diameter of the gate 0'04 to 0'06 ; length of the spines O'OIS to 0'026.
Habitat. — Tropical Atlantic, Station 338, depth 1990 fathoms.
4. Zygocircus rhombicus, n. sp.
Gate rhombic. King rhombic, with three prominent edges, and eight short conical curved spines arising from the lateral edges at the four corners of the rhombus. The basal and ventral spine are larger than the apical and dorsal spine ; the ventral rod is more curved (with smaller angle) than the shorter dorsal rod. The medial edge of the ring is smooth, without spines.
Dimensions. — Diameter of the gate 0'08 ; length of spines 0'02 to 0'04.
Habitat. — South Atlantic, Station 335, depth 1425 fathoms.
5. Zygocircus pentagonus, n. sp. (PL 81, fig. 8). •
Gate roundish pentagonal. King very thick (about as thick as the radius of the gate), irregularly pentagonal, with prominent sagittal edge. On both sides of the latter arise at the five corners five pairs of short simple irregularly curved spines. The four ventral spines are larger than the four dorsal, and the two basal spines larger than the eight former, forked. (In fig. 8 the basal spines are turned upwards.)
Dimensions. — Diameter of the gate O'O1? ; length of the spines 0'04 to 0'06.
Habitat. — Central Pacific, Station 268, depth 2900 fathoms.
REPORT ON THE RADIOLARIA. 947
6. Zygocircus hexagonus, n. sp.
Gate irregularly hexagonal. Ring obliquely hexagonal, thick, without edges, with six short and stout conical spines on the six corners. The two spines of the curved ventral rod are longer than the two spines of the straight dorsal rod. The apical spine is smaller and the basal spine larger than the four others.
Dimensions. — Diameter of the gate 0'07 to 0'09 ; length of the spines O'Ol to O03.
Habitat. — North Pacific, Station 241, depth 2300 fathoms.
7. Zygocircus triquetrus, n. sp. (PL 81, fig. 3).
Gate obliquely ovate. King obliquely hexagonal, with three sharp edges and three short conical spines on each of the six corners. Therefore each hexagonal edge bears six short radial spines of -equal size.
Dimensions. — Diameter of the gate 0'04 to 0'08 ; length of the spines O'Ol to 0'02.
Habitat. — Cosmopolitan ; Mediterranean, Atlantic, Pacific, surface.
8, Zygocircus dodecanthus, n. sp.
Gate semicircular. Eing semicircular or irregularly hexagonal, without edges, with twelve short blunt spines, arising in pairs from the six corners ; two apical, two basal, and between them two equatorial corners. Three pairs of spines remain on the straight dorsal rod, three on the curved ventral rod.
Dimensions. — Diameter of the gate 0'04 to 0'06 ; length of the spines O'Ol to 0'02.
Habitat. — Central Pacific, Stations 263 to 268 ; depth 2650 to 2900 fathoms.
9. Zygocircus acacia, n. sp. (PI. 81, fig. 5).
Gate obliquely ovate. Eing semi-ovate, with straight dorsal and curved ventral rod, partly with distorted edges. Six bunches of numerous short and straight conical spines arise from the ring, one larger bunch (often trifid) from the apex, two smaller bunches from the dorsal, two from the ventral rod, and one very large bunch from the base. The six bunches are often more separated, smaller, and the spines shorter than in the figured specimen, which passes over into Dendrocircus.
Dimensions. — Diameter of the gate 012 to 016 ; length of the spines, O'Ol to 0'07.
Habitat. — Central Pacific, Station 266, depth 2750 fathoms.
10. Zygocircus polygonus, n. sp. (PL 81, fig. 2).
Gate irregularly roundish or ovate. Eing irregularly polygonal or sometimes nearly circular, without edges, armed with a single series of ten to fifteen short pyramidal spines, which are irregularly
948 THE VOYAGE OF H.M.S. CHALLENGER.
disposed in the sagittal plane. The ventral rod is strongly curved, often semicircular, the dorsal rod less curved or nearly straight.
Dimensions. — Diameter of the gate 0'05 to O07 ; length of the spines 0'004 to 0'02.
Habitat. — Cosmopolitan — Atlantic, Pacific ; also fossil in Barbados.
11. Zygocircus biitschlii, n. sp.
Zygocircus produdus, Biitschli, 1882, Zeitsehr. f. wiss. Zool., vol. xxxvi. p. 497.
Grate obliquely ovate. King irregularly roundish, semi-ovate or ovate, with interrupted and distorted edges, and with a large number (ten to twenty or more) of simple, irregularly formed and asymmetrically disposed spines ; commonly some larger spines at the base.
Dimensions. — Diameter of the gate 0'05 to 0'09 ; length of the spines O'OOS to 0'02.
Habitat. — Fossil in Barbados.
12. Zygocircus productus, Biitschli.
Zygocircus productus, Biitschli, 1882, Zeitsehr. f. wiss. Zoo]., vol. xxxvi. p. 496. Lithoeircus productus, R. Hertwig, 1879, Organismus d. Radiol., p. 69, Taf. vii. fig. 4.
Gate obliquely ovate. Eing obliquely ovate, with three complete prominent edges and with numerous (ten to twenty or more) simple, short conical spines, arising in three series from the three edges ; commonly some smaller spines at the base.
Dimensions. — Diameter of the gate 01 to 0'2 ; length of the spines 0'005 to 0'02.
Habitat. — Cosmopolitan ; Mediterranean, Atlantic, Pacific, surface.
Genus 404. Dendrocircus,1 Haeckel, 1881, Prodromus, p. 447.
Definition. — S tephanida with a simple dipleuric or bilateral ring, armed with branched spines, without typical basal feet.
The genus Dendrocircus has the same dipleuric or bilaterally symmetrical form of the sagittal ring as its ancestral genus Zygocircus. It differs from the latter in the development of branched radial spines, and therefore bears to it the same relation as the amphithect Lithoeircus does to the simpler Archicircus.
1. Dendrocircus quadrangulus, n. sp.
Gate irregularly quadrangular or nearly semicircular. Ring quadrangular, edgeless, with four unequal sides ; ventral rod more curved and with longer sides than the dorsal rod. From the four edges arise four strong, irregularly branched spines, about as long as the diameter of the gate,
1 De7idroaYctts=Ring bearing trees ; 8si/8jo», xloxo;.
REPORT ON THE RADIOLARTA. 949
with curved branches; the ventral and basal spines larger than the dorsal and apical spines. Similar to Lithocircus quadricornis (PI. 81, fig. 9), but less branched, and with a striking difference between the shorter dorsal and the longer ventral rod.
Dimensions. — Diameter of the gate 0-04 to 0'06 ; length of the spines O05 to 0'07.
Habitat. — North Pacific, Station 256, depth 2950 fathoms.
2. Dendrocircus dodecarrhiza, n. sp.
Gate obliquely ovate. Ring irregularly quadrangular, with three prominent edges. From the latter arise at the four corners twelve divergent, irregularly branched spines (three in each corner), about as long as the radius of the gate, with curved branches ; the three basal spines larger than the nine others.
Dimensions. — Diameter of the gate 0'08 to 01 ; length of the spines 0'04 to 0'06.
Habitat. — Indian Ocean (Maldive Islands), surface (Haeckel).
3. Dendrocircus dodecancistra, n. sp. (PI. 81, fig. 11).
Gate obliquely ovate or nearly elliptical. Ring irregularly ovate, with three distorted edges and six pairs of branched spines. The two ventral pairs are much more distant than the two dorsal pairs, the ventral rod being longer and more curved than the dorsal rod. All twelve spines are of nearly equal size, are more or less curved, about as long as the diameter of the gate, and each bears six to twelve irregular short branches at the end.
Dimensions. — Diameter of the gate 0'07 to 0'08 ; length of the spines O05 to 0'08.
Habitat. — Tropical Atlantic, Station 342, depth 1445 fathoms.
4. Dendrocircus arborescens, n. sp. (PL 81, fig. 10).
Gate irregularly roundish or nearly circular. Ring of the same form, with slight edges and" six pairs of elegant arborescent spines (one apical, two dorsal, two ventral, and one basal pair) ; the three latter somewhat larger than the three former. Each tree is larger than the ring, in the basal half simple, in the distal half forked, each fork-branch with numerous dichotomous terminal branches.
Dimensions. — Diameter of the gate 0'06 to 0'08 ; length of the spines 012 to 015.
Habitat. — Central Pacific, Stations 266 to 274, surface.
5. Dendrocircus elegans, n. sp. (PI. 81, fig. 13)-
Gate irregularly ovate. Ring thick, ovate, with three denticulate edges and six bunches of stout, branched and spinulate, curved spines. The four ventral spines are more distant than the four dorsal, the ventral rod being more curved than the dorsal The latter bears above the two apical spines. The two basal spines are much larger, deeply forked ; their four fork-branches may be compared to the four basal feet of Stephanium.
Dimensions. — Diameter of the ring 0'09 to Oil; length of the spines 0'03 to 0'06.
Habitat. — Central Pacific, Station 274, depth 2750 fathoms.
950 THE VOYAGE OF H.M.S. CHALLENGER.
6. Dendrocircus barbadensis, n. sp.
Gate irregularly ovate or nearly semicircular. King of the same oblique form, thick, with interrupted and distorted edges, armed with eight to twelve larger irregularly formed and branched acute spines ; between them numerous conical smaller spines. This common species is very polymorphous and variable.
Dimensions. — Diameter of the ring 0'05 to 0'08 ; length of the spines O'OOS to 0'02.
Habitat. — Fossil in Barbados.
7. Dendrocircus stalactites, n. sp. (PL 81, fig. 14).
Gate obliquely ovate. King irregularly ovate or roundish, very thick, without edges, armed with numerous (eight to twelve or more) short and stout branches, which are shorter than the diameter of the gate, irregularly disposed and branched, with very numerous clustered blunt ramules.
Dimensions. — Diameter of the gate 0'07 to 0'09 ; length of the spines 0'02 to 0'06.
Habitat. — Western Tropical Pacific, Station 225, depth 44*75 fathoms.
Subfamily 2. CORTINIDA, Haeckel. Definition. — S tephanida with typical basal feet (or cortinar feet).-
Genus 405. Cortina,1 n. gen.
Definition, — S tephanida with a simple dipleuric or bilateral ring, bearing at the base three divergent feet (one odd caudal and two paired lateral feet).
The genus Cortina, and the following Stcphanium represent together the small but very important group of Cortinida, differing from the simple Lithocircida in the possession of three typical basal feet, which are transmitted to the majority of the NASSELLARIA by heredity, and produce their peculiar triradial structure. They appear therefore as a combination of the simple ring (Zygocircus) with three basal feet (Plagonium). One of these three divergent feet is the odd caudal foot, opposite to the apical horn ; the two others are the paired lateral or pectoral feet. (On the probable origin and the typical signification of Cortina compare above, pp. 891—894.)
.1.- Cortina tripus, n. sp. (PI. 83, fig. 9).
.King ovate, smooth, or with a few short thorns. Apical horn oblique, curved, simple, smooth, about as long as the sagittal axis of the ring. Feet divergent, curved, simple, smooth, about as
1 Cortina = Tripod.
REPORT ON THE RADTOLARIA. 951
long as the horn ; the caudal foot shorter than the two pectoral feet Very variable in form and size.
Dimensions. — Height of the ring 0'06 to 0'09, breadth 0'04 to 0'06 ; length of the feet 0'05 to 01.
Habitat. — Cosmopolitan ; Atlantic, Indian, Pacific, surface and in various depths.
2. Cortina typus, n. sp. (PI. 97, fig. 1).
Eing kidney-shaped or nearly semicircular, with revolute vertical dorsal rod and strongly curved ventral rod ; both rods with two pairs of spine-bunches. Apical horn nearly straight, thorny, longer than the ring, directed a little obliquely backwards. Feet slightly curved, of equal length, two .to three times as long as the ring ; each armed with few large bunches of curved spines, which are more developed in the caudal foot than in the two pectoral feet.
Dimensions. — Height of the ring 014, breadth 0'08 ; length of the feet 0'2 to 0;3>
Habitat. — Tropical Atlantic, Station 348, depth 2450 fathoms.
3. Cortina conifera, n. sp.
Eing subcircular, smooth. Apical horn and the three divergent feet of equal size and similar form, cylindrical, straight, about as long as the ring, at the distal end thickened, with a dimply cone (similar to Tripospyris conifera and Tripospyris eucolpa, PL 84, figs. 4, 7).
Dimensions. — Height of the ring 0'08, breadth 0'06 ; length of the feet 0'09.
Habitat. — Central Pacific, Station 268, depth 2900 fathoms.
4. Cortina furcata, n. sp.
Eing elliptical, with three forked horizontal spines (one on the dorsal and two on the ventral rod). Apical horn and the three divergent feet of equal size, somewhat longer than the ring, slightly curved, in the distal half forked.
Dimensions. — Height of the ring 0'07, breadth 0-05 ; length of the feet O'OQ.
Habitat. — South Atlantic, Station 332, depth 2200 fathoms.
5. Cortina dendroides, n. sp.
Eing ovate, with six pairs of branched horizontal spines, three on the dorsal and three on the ventral rod. Apical horn very large, arborescent, about as long and as broad as the ring. Feet similar to the horn, also richly branched, of equal size. All the rods and their branches curved, with prominent distorted edges.
Dimensions. — Height of the ring 013 to 017, breadth 01 to 012; length of the feet 01'5 to 0-2.
Habitat. — Central Pacific, Stations 266 to 274, depth 2350 to 2925 fathoms.
952 THE VOYAGE OF H.M.S. CHALLENGES.
6. Cortina cervina, n. sp. (PI. 92, fig. 21).
Eing ovate, with four pairs of forked horizontal spines (two dorsal and two ventral pairs) Apical horn straight and stout, as long as the ring, with trifid point. Three feet equal, widely divergent, very large, branched like a deer's antler, with very numerous short and stout, curved and pointed branches. All rods and branches roundish, without edges.
Dimensions. — Height of the ring 01, breadth 0'07 ; length of the feet 012 to 016.
Habitat. — Central Pacific, Station 265, depth 2900 fathoms.
Genus 406. Stephanium,1 n. gen.
Definition. — S tephanida with a simple dipleuric or bilateral ring, bearing at the base four divergent feet (two sagittal and two lateral feet).
The genus Stephanium differs from the preceding nearly allied Cortina in the production of four basal feet ; the new foot, missing in the latter, is the anterior or sternal foot. Therefore Stephanium may be regarded as the archetype of all those NASSELLARIA in which, on the base of the sagittal ring, there are developed four typical feet — two sagittal feet (the posterior caudal and anterior sternal foot) and two lateral feet (right and left). On the origin of Stephanium compare above, p. 893, &c.
1. Stephanium quadrupes, n. sp. (PI. 92, fig. 20).
Ring ovate, with three prominent dentate edges and a short pyramidal apical horn. Four feet all of nearly equal size, about as long as the ring, also with three thorny edges, in the upper half divergent, in the lower convergent.
Dimensions. — Height of the ring 012, breadth 0'08 ; length of the feet Oil to 013.
Habitat. — Central Pacific, Station 266, depth 2750 fathoms.
2. Stephanium tetrapus, n. sp.
Ring elliptical, without edges, thorny, with a stout, thorny apical horn of the same length. Four feet curved and irregularly branched, divergent, of different size. The two sagittal feet (the anterior sternal and posterior caudal) about as long as the ring. The two lateral feet (right and left) nearly twice as long, more richly branched.
Dimensions. — Height of the ring 016, breadth Oil ; length of the feet 015 to 0'3.
Habitat. — Central Pacific, Station 272, depth 2600 fathoms.
1 Stephanium= Small crown or garland ; att<fa.tiiiiv.
REPORT ON THE RADIOLARIA. 953
Family XLIX. SEMANTIDA, n. fam.
Definition. — S tephoidea with a single vertical ring (the primary sagittal ring), bearing on its base a horizontal ring (basal or cortinar ring) with two to four or more basal gates (or cortinar pores).
The family Semantida differs from the preceding Stephanida in the development of a small horizontal ring oh the base of the primary vertical sagittal ring. By the crossing of these two rings a small latticed basal plate is formed, with one or two pairs of pores ; rarely with a greater number of " basal pores." The production of this characteristic " basal plate " is of the greatest morphological importance, as the beginning of the numerous different lattice-formations, which are differentiated in the great majority of NASSELLARIA.
In my Prodromus (1881, p. 446) I had enumerated the Semantida with three genera (Nos. 298 to 300) as a separate subfamily of the Dyostephida or " Stephoidea biannularia," and characterised these " Dyostephanida " by the following definition : " Skeleto annulis duobus composite, qui in duobus planis invicem perpendicularibus jacent ; altero annulo (sagittali) verticali, altero (basali) horizontali." As the names there given were already employed with another signification, and as the Zygostephanida (there united with the Dyostephanida) are more closely related to the Coronida, I now change the names, and propose to call the family Semantida, expressing by this term the typical similarity of the skeleton to a signet-ring (Semantis, Semantrum, Semantidium).
At about the same time, some Stephoidea of this family were accurately described by Biitschli (1882, Zeitschr. f. wiss. Zool., vol. xxxvi. p. 495, Taf. xxxii. figs. 6, 7, 8). He called them Stephanolithis, a name which Ehrenberg had em- ployed, not for complete shells of Kadiolaria, but for isolated parts of such, and for siliceous fragments of different skeletons, needles of Sponges, &c. The three species described by Biitschli represent three different genera of our Semantida, viz., Semantis spinescens (with two gates in the basal plate), Semantrum mulleri (with four gates), and Semokntidium haeckelii (with six gates). He pointed out the great morpho- logical value of the fenestrated basal plate and its paired gates, as beginnings of numerous other NASSELLARIA. But his opinion, that in all S p y r o i d e a and C y r- t o i d e a, derived from these, two pairs of basal gates were constant, was erroneous, nor was the formation of the first pair naturally explained ; he supposed that the formation of the basal plate begins by development of an odd sagittal apophysis, arising from the base of the primary sagittal ring. But this odd sagittal apophysis (" der unpaare mediane Kieselfortsatz cl", loc. cit., p. 497) is in reality not a primary
(ZOOL. CHALL. BXP. — PART XL. — 1886.) Hi1 120
954 THE VOYAGE OF H.M.S. CHALLENGER.
and essential part of the skeleton, but secondary and of little morphological value, absent in the majority of the Semantida and of the other NASSELLARIA.
We divide our family Semantida into two different subfamilies, which possibly possess a direct phylogenetic relation to the two subfamilies of Stephauida : — The Semantiscida have no typical feet, and have arisen directly from the Lithocircida ; the Cortiniscida, however, possess the three typical basal feet of Cortina, and may there- fore be derived directly from the Cortinida. Since these three cortinar feet are probably identical with the three primary radial rods of the Plectoidea, an imme- diate affinity also to these NASSELLARIA is indicated.
The Semantiscida, which do not possess these three basal cortinar feet, are the simpler forms of the family. The simplest of all, and perhaps the common ancestral form of the whole family, is Semantis (PI. 92, figs. 1, 2). It may be derived from Archicircus or Zygocircus by development of two pairs of horizontal apophyses on its base, around the porochora of the central capsule. The two rods of each side (right and left), becoming curved one towards the other, and meeting laterally, form a simple horizontal gate, and the two paired basal gates together, a horizontal ring or basal ring, to which the primary sagittal ring is perpendicular. In the next allied genus, Semantrum (PL 92, figs. 3—5), three pairs of horizontal apophyses are developed, and therefore two pairs of basal gates produced, an anterior and a posterior. In the third genus, Semantidium (PL 92, figs. 6, 7), three pairs of basal pores or gates are visible, surrounded and separated by four pairs of horizontal apophyses, which arise from the base of the sagittal ring. Finally, in Clathrocircus (PL 92, figs. 8—10) the number of apophyses is much increased, and two parallel rows of pores are developed along the two sides of the sagittal ring.
The basal plate or the "seal," developed from the base of the primary sagittal ring or " signet-ring," is therefore a horizontal ring, which becomes bisected by the latter, and exhibits either one pair of primary " basal gates " or two or three pairs of these important basal pores, rarely more. Since these pores possess the greatest morphological value, and are probably everywhere homologous, we give to them and to the separating apophyses certain names, and call the anterior pair of gates, "jugular pores " (i in our figures, the pair I of Biitschli) ; the middle (usually the largest) pair, " cardinal pores " {& in our figures, the pair II of Biitschli), and the posterior, smaller pair, " cervical pores," I. The typical pairs of rods, by the union of which these basal pores arise, are the following : — (1) the clavicular or furcular rods,/, the first pair (rods el of Biitschli), (2) the coracal rods, e, between the jugular and cardinal pores (rods e of Biitschli), (3) the scapular rods, g, between the cardinal and cervical pores (rods e2 of Biitschli), (4) the cervical rods, the fourth pair of apophyses, the most posterior, h. Biitschli supposes that the topographical succession of the three typical pairs of basal pores is also the chronological succession, the jugular being formed first, the
KEPORT ON THE RA.DIOLARIA. 955
cardinal second, and the cervical pores third ; but it seems that this succession is often altered, and that the cardinal pores (the largest), appear first, the jugular pores (in front of them) second, and the cervical pores third (or perhaps sometimes in the inverse succession).
The Cortiniscida, the second subfamily of Semantida, differ from the preceding Semantiscida in the possession of three typical basal feet, which are probably inherited from the Cortinida, and perhaps indirectly from the Plagonida (Plagoniscus). The simplest and the most important form of this second family is Cortiniscus (PI. 92, figs. 11—13), differing from its probable ancestral form, Cortina, in the development of a basal ring, produced by horizontal union of the basal apophyses. The three typical feet are the same as in all triradiate NASSELLARIA, two paired pectoral feet (p^, _pn) diverging on the anterior base of the sagittal ring, whilst the odd caudal foot (c) lies on its posterior base in the sagittal plane and appears as a basal prolongation of the dorsal rod of the sagittal ring ; the upper part of the dorsal rod is usually prolonged into an ascending apical horn. In Stephaniscus (PI. 92, figs. 14, 15) four basal feet are visible, an anterior or sternal foot (z) being added as a prolongation of the basal rod of the ring, opposite to the caudal foot. Finally, Semantiscus (PL 92, figs. 16—18) is distinguished by the possession of six divergent basal feet, probably identical with those of all six-radiate NASSELLARIA ; three of these may be regarded as primary and per- radial, the odd caudal and the paired pectoral feet; the three other intercalated as secondary or interradial feet, the odd sternal (z) and the paired tergal feet (^, tn).
The basal plate of these Cortiniscida exhibits the same important differences as in the preceding Semantiscida, either one, or two, or three pairs of basal gates being developed. But there occur also in some species (mainly in Cortiniscus) only three basal gates, an odd anterior (between the two pectoral feet and a connecting horizontal bar), and two paired posterior (between the two pectoral and the odd caudal foot). It requires further accurate researches to solve the important problem, what the true homologies of these typical basal pores and the separating bars are in the different genera of Semantida. In Semantiscus there are three pairs of basal pores in the horizontal seal, correspond- ing to those of Semantidium, and the radial rods or bars between these are the basal parts of the six radial feet ; therefore the odd caudal foot (t) seems to be the posterior, and the odd sternal foot (z) the anterior prolongation of the basal part of the primary sagittal ring; the two paired anterior or pectoral feet (jov pn) the prolongations of the coracal rods (e) and the two paired posterior or tergal feet (tlt <n), the prolongations of the scapular rods (g). But it is not yet certain whether these six radial feet and the separating gates of the basal plate are all the same and truly homologous in all six- radiate NASSELLARIA. In every case the comparative study of the Semantida is of the highest value for the accurate knowledge of the MONOPYLEA.
956
THE VOYAGE OF H.M.S. CHALLENGER.
I. Subfamily
Semantiscida.
Basal ring without typical, regularly disposed basal feet (no cortinar feet).
II. Subfamily
Cortiniscida.
Basal ring with typical, regularly disposed basal feet (cortinar feet).
Synopsis of the Genera of Semantida.
{Two basal pores, . Four basal pores, . Six basal pores,
Besides four basal pores, also apical pores or dorsal and ventral pores along the whole ring,
Three basal feet.
Four basal feet.
Six basal feet.
One odd caudal foot and two paired lateral feet, .
f Two sagittal and two lateral
I or pectoral feet,
f Two sagittal, two pectoral,
( and two tergal feet,
407. Semantis.
408. Semantrum.
409. Semantidium.
410. ClatJirocircus.
411. Gortiniscus.
412. Stephaniscits.
413. Semantiscus.
Subfamily 1. SEMANTISCIDA, Haeckel. Definition. — S emantida without typical basal feet or cortinar feet.
Genus 407. Semantis,^ n. gen.
Definition. — S emantida with two basal pores (or jugular pores), without typical basal feet.
The genus Semantis, the most primitive and the oldest of the Semantida, is of the greatest morphological interest, as the first form of Stephoidea which produces gates or pores by communicating branches, and therefore the probable ancestral form not only of this family, but of the greater number of all Stephoidea, and perhaps even of all Spyroidea and Cyrtoidea. Semantis arises from Archicircus by the pro- duction of two pairs of lateral branches from the basilar rod of the sagittal ring, one anterior pair of clavicular rods, and one posterior pair of coracal rods. By junction of the clavicular and coracal rod on each side arises a left and a right pore, the "jugular pore or jugular gate."
1. Semantis biforis, n. sp. (PI. 92, fig. 2).
Sagittal ring obliquely ovate, nearly trapezoidal, with six pairs of short marnmillated knots or branches ; dorsal rod straight, vertical, with two pairs of knobs, ventral rod strongly convex, also with
1 Semantis = Signet-ring ;
EEPORT ON THE RADIOLARIA. 957
two pairs of knobs ; two other pairs in the apical rod. Basilar rod horizontal, straight. Basal ring with six pairs of similar knobs, three on each side. Basal gates ovate or nearly triangular.
Dimensions. — Height of the sagittal ring O09, breadth 0'07.
Habitat. — Central Pacific, Stations 265 to 268, depth 2700 to 2900 fathoms.
2. Semantis distoma, n. sp.
Sagittal and basal ring nearly of the same form as in the preceding species, but half as thick and armed with numerous branched spines which are about half as long as the diameter of the main gate, and with thin and curved pointed branches.
Dimensions. — Height of the sagittal ring O'll, breadth 0'08.
Habitat. — North Pacific, Station 244, depth 2900 fathoms.
3. Semantis dipyla, n. sp.
Sagittal ring kidney-shaped, very thick, with six pairs of short, thorny, or irregularly tuberculated knobs (two dorsal, two apical, and two ventral pairs). Basal ring smooth, scarcely half as thick, horizontal, with two semicircular basal gates, about half as broad as the main gate. From the two opposite lateral corners of the basal ring two slender upwardly curved spines arise, resembling the basal part of a commencing frontal ring.
Dimensions. — Height of the sagittal ring 0'08, breadth 0'05.
Habitat. — Western Tropical Pacific, Station 225, depth 4475 fathoms.
4. Semantis sigillum, n. sp. (PI. 92, fig. 1).
Sagittal ring elliptical, with four pairs of stout arborescent spines (two apical and two equatorial pairs), which are irregularly branched and forked, with numerous thin lateral branches. Apex with a short conical trifid vertical horn. Basal ring thorny, with obliquely descending slightly curved bars.
Dimensions. — Height of the sagittal ring 012, breadth 0'09.
Habitat. — South Pacific, Station 300, depth 1375 fathoms.
5. Semantis distephanus, n. sp. (PL 83, fig. 3).
Sagittal ring thin, semicircular, smaller than the thin basal ring, which exhibits two semi- circular gates. Both rings are armed with numerous small spines of equal size, which on the former are arranged in two, on the latter in three regular rows. (The basal rod of the sagittal ring, separating the two basal gates, in fig. 3 is, by mistake, not distinctly enough drawn.)
Dimensions. — Height of the sagittal ring 0'06, breadth 0'08.
Habitat. — Tropical Atlantic, Station 348, surface.
958 THE VOYAGE OF H.M.S. CHALLENGER.
6. Semantis spinescens, Haeckel.
StepTianolithis spinescens, Elirenberg, 1875, Abhandl. d. k. Akad. d. Wiss. Berlin, p. 160, Taf.
i. fig. 29. StepUanolithis spinescens, Biitschli, 1882, Zeitschr. f. wiss. Zool., vol. xxxvi. p. 497, Taf. xxxii.
figs, la, 76.
Sagittal ring ovate, with four pairs of thin, irregularly branched spines, two apical pairs, one on the straight dorsal rod, and one on the curved ventral rod. Basilar rod with a posterior and an anterior forked rod (commencing caudal and sternal foot). Basal ring square, with two lateral spines, and .two triangular gates scarcely one-third as broad as the ring-gate. An internal ascend- ing procolumna (rod q in the figure of Biitschli) connects the basal and ventral rods of the sagittal ring.
Dimensions. — Height of the sagittal ring 01, breadth 0'07.
Habitat. — Fossil in Barbados.
Genus 408. Semantrum,1 n. gen.
Definition. — S emantida with four basal pores (two anterior jugular and two posterior cardinal pores), without typical basal feet.
The genus Semantrum, one of' the most important of the NASSELLARIA, arises from the preceding Semantis by duplication of the two basal gates. Behind the pair of coracal rods there arises from the basilar rod of the sagittal ring a third pair of lateral horizontal branches, the scapular rods. These become connected with the coracal rods on each side, and so produce a second posterior pair of basal pores, the " cardinal gates." These are constantly larger than the anterior "jugular gates." Therefore the vertical ring of Semantrum possesses a horizontal basal ring with four very characteristic gates, enclosed by three pairs of lateral curved and connected branches, and these become transmitted by heredity to the majority of the NASSELLAKIA.
1. Semantrum quadrifore, n. sp. (PI. 92, fig. 5).
Sagittal ring subcircular or ovate, with three edges and four sagittal forked spines on the odd edge (two dorsal and two ventral spines). Basal ring decagonal, with ten simple or forked spines on the ten corners. Jugular gates tetragonal. Cardinal gates pentagonal.
Dimensions. — Height of the sagittal ring 009, breadth 0'07.
Habitat. — Tropical Atlantic, Station 351, surface.
1 Semantrum= Signet-ring ;
REPORT ON THE RADIOLARIA. 959
2. Semantrum tetrastoma, n. sp. (PI. 92, fig. 3).
Sagittal ring semicircular, thorny, without edges. Basal ring tetragonal or nearly cordate, with a small anterior and a large posterior bow-shaped incision ; on the lateral edges with numerous irregular thorns. Jugular gates pear-shaped. Cardinal gates nearly kidney-shaped.
Dimensions. — Height of the sagittal ring O'l to 0'14, breadth 0'07 to 0'09.
Habitat. — Central Pacific, Stations 265 to 268, depth 2700 to 2900 fathoms.
3. Semantrum tetrapylum, n. sp.
Sagittal ring elliptical, tuberculate. Basal ring trapezoidal, also with roundish thick rods and small irregular tubercles on the margin. Jugular gates ovate, two-thirds as broad as the triangular cardinal gates.
Dimensions. — Height of the sagittal ring O'OS, breadth O'Oo.
Habitat. — North Pacific, Station 253, depth 3125 fathoms.
4. Semantrum mulleri, Haeckel.
Stephanolithis mulleri, Biitschli, 1882, Zeitschr. f. wiss. Zool., vol. xxxvi. pp. 499, 539, Taf. xxxii. figs. 8a, 8b, So.
Sagittal ring nearly semicircular or obliquely ovate, thorny. Basal ring also nearly semicircular, with two slight sagittal incisions (one anterior and one posterior), on the lateral edges with numerous small thorns. Jugular pores (pair I of Biitschli) pear-shaped. Cardinal pores (pair IT. of Biitschli) triangular. Sometimes (but not constantly) a pair of cervical bows connects the scapular bars with the subvertical dorsal rod of the sagittal ring.
Dimensions. — Height of the sagittal ring 0-09, breadth 0'06.
Habitat. — Fossil in Barbados.
5. Semantrum sphragisma, n. sp.
Sagittal ring circular, smooth. Basal ring also nearly circular and smooth ; its four basal gates of nearly equal size, elliptical or subcircular ; the jugular pores scarcely smaller than the cardinal pores. All rods smooth, cylindrical, without edges and thorns.
Dimensions. — Height of the sagittal ring O'OS, breadth 0'07.
Habitat. — Tropical Atlantic, Station 347, depth 2250 fathoms ; also fossil in Barbados.
G. Semantrum biitschlii, n. sp.
Sagittal ring triangular, with vertical straight ascending dorsal rod, horizontal straight basilar rod and obliquely ascending, slightly curved ventral rod ; all rods nearly cylindrical, with irregular
960 THE VOYAGE OF H.M.S. CHALLENGER.
branched thorns and distorted edges. Jugular pores triangular, scarcely half as broad as the large semicircular cardinal pores.
Dimensions. — Height of the sagittal ring Oil, breadth 0'08.
Habitat. — Fossil in Barbados.
7. Semantrum signarium, n. sp. (PL 92, fig. 4).
Sagittal ring obliquely ovate, thorny. Basal ring kidney-shaped or nearly pentagonal, with broad concave dorsal incision and five larger branched spines on the five corners ; between them smaller thorns. Jugular gates pear-shaped, scarcely half as broad as the triangular cardinal gates.
Dimensions. — Height of the sagittal ring 012, breadth OD9.
Habitat. — Central Pacific, Station 271, depth 2425 fathoms.
Genus 409. Semantidium, n. gen.
Definition. — S emantida with six basal pores (two anterior jugular, two middle cardinal, and two posterior cervical pores), without typical basal feet.
The genus Semantidium exhibits a further developmental stage of the basal plate of the Semantida. Whilst this plate in Semantis possesses one pair of basal pores, and in Semantrum two pairs, here in Semantidium it has three pairs. The new third pair is produced on the dorsal edge of the basal plate, which becomes connected with the basal part of the dorsal rod of the sagittal ring by a pair of cervical rods. The middle pair of pores (the cardinal) are always larger than the anterior (jugular) and the posterior (cervical pores). The same form of basal plate is preserved in numerous Spyroidea and C y r t o i d e a, as .a " cortinar septum with six collar pores," (e.g., PI. 53, fig. 18).
1. Semantidium hexastoma, n. sp. (PI. 92, fig. 6).
Sagittal ring ovate, thorny. Basal ring rhombic or nearly square, with four short conical descending spines on the four prominent edges (two sagittal and two lateral) ; between them numerous smaller irregular thorns. Jugular and cervical gates nearly equal, ovate, half as broad as the triangular cardinal gates between them.
Dimensions. — Height of the sagittal ring 014, breadth 01.
Habitat. — Central Pacific, Station 265, depth 2900 fathoms.
2. Semantidium sexangulum, n. sp.
Sagittal ring ovate, with six pairs of short branched thorns (two apical, two dorsal, and two ventral). Basal ring hexagonal, with three pairs of short branched thorns on the six corners (one
1 Semantidium= Small signet-ring; v(itu.a.niti<nt.
REPORT ON THE RADIOLARIA. 961
sagittal pair, one posterior and one anterior). All six gates of the basal plate triangular, the jugular and cervical a little smaller than the cardinal gates.
Dimensions. — Height of the sagittal ring O'l, breadth 0'07.
Habitat. — Tropical Atlantic, Station 348, depth 2450 fathoms.
3. Semantidium haeckelii, Biitschli.
Stephanolithis Haeckelii, Biitschli, 1882, Zeitschr. f. wiss. Zool., vol. xxxvi. pp. 499, 538, Taf. xxxii. figs. 6a, 6ft.
Sagittal ring elliptical, with three pairs of short horizontal branched spines, one apical and two equatorial pairs (one dorsal and one ventral). Basal ring roundish hexagonal, with numerous short thorns on the margin. Jugular pores ovate, about half as broad as the ovate cardinal pores and twice as broad as the small cervical pores.
Dimensions. — Height of the sagittal ring 0'08, breadth 0'06.
Habitat. — Fossil in Barbados.
4. Semantidium signatorium, n. sp. (PI. 92, fig. 7).
Sagittal ring semicircular, thorny ; basal ring pentagonal, with short spines on the margin and five stronger thorny spines on the five corners. Jugular pores ovate, smaller than the triangular cervical pores. Cardinal pores two to three times as large as each of the former, pentagonal.
Dimensions. — Height of the sagittal ring 0'08, breadth 0'12.
Habitat. — North Pacific, Station 241, depth 2300 fathoms.
Genus 410. Clathrocircus,^ Haeckel, 1881, Prodromus, p. 447.
Definition. — Semantida with a variable number of pores on the apical and the basal part of the ring, symmetrically arranged, without typical basal feet.
The genus Clathrocircus comprises those Semantida in which the sagittal ring bears not only basal pores (as in the three preceding genera) but also apical pores (on the opposite pole of the main axis), or a variable number of pores along the whole ring. All these pores are symmetrically arranged in pairs. In the simplest form there are only two apical pores opposite to four basal pores, whilst in the highest state of development the whole ring bears two complete circles of pores. At both poles of the transverse axis two large lateral gates remain open. If these become closed by lattice-work, Clathrocircus passes over into Dictyospyris.
1 Clathrocircus — Lattice-ring; xx»jfy>(», KI'^KO;.
(ZOOL. CHALL. EXP. — PABT XL. 1886.) Rr 121
962 THE VOYAGE OF H.M.S. CHALLENGER.
1. Clathrocircus hexaporus, n. sp.
Sagittal ring circular, smooth, with three pairs of pores (one apical and two basal). The two apical pores are triangular, with two lateral spines, and correspond to the two mitral gates of the Tympanida. The four basal pores form a hexagonal basal plate, with six lateral spines, and correspond to the four basal pores of Semantrum; the two jugular are pear-shaped, and half as broad as the two triangular cardinal pores.
Dimensions. — Height of the sagittal ring 0'08, breadth 0'06.
Habitat. — Cosmopolitan ; Atlantic, Pacific, many Stations, surface.
2. Clathrocircus octoporus, n. sp.
Sagittal ring elliptical, smooth, with four pairs of pores (two apical and two basal). The four apical pores are of nearly equal size, subcircular, and form a regular cross around the apical pole. The four basal pores are ovate, and form a quadrangular plate, armed with marginal thorns ; the two jugular pores are somewhat smaller than the two cardinal pores.
Dimensions. — Height of the sagittal ring Oil, breadth 0'08.
Habitat. — Tropical Atlantic, Station 348, depth 2450 fathoms.
3. Clathrocircus decaporus, n. sp.
Sagittal ring ovate, thorny, with five pairs of pores (two apical and three basal). The four apical pores are roundish and form a cross. The six basal pores are triangular and form a hexagonal plate with thorny margin ; the two jugular pores are somewhat larger than the two cervical, and half as broad as the two cardinal pores.
Dimensions. — Height of the sagittal ring 0'09, breadth 0-07.
Habitat. — North Pacific, Station 256, depth 2950 fathoms.
4. Clathrocircus stapedius, n. sp. (PI. 92, fig. 8).
Sagittal ring ovate, smooth, with six pairs of pores (two apical and four basal). The four apical pores are of nearly equal size and form a quadrangular mitral plate with two large lateral horns. The eight basal pores are of very different size (the four central far larger than the two anterior and the two posterior), and form a hexagonal basal plate, also with two large lateral horns. The four branched lateral horns (two upper and two lower) form together an incomplete frontal ring.
Dimensions. — Height of the sagittal ring 01, breadth 0'08.
Habitat. — Central Pacific, Station 271, depth 2425 fathoms.
REPORT ON THE RADIOLARIA. 963
5. Clathrocircus dictyospyris, n. sp. (PL 92, fig. 9).
Sagittal ring ovate, thorny, with eight pairs of pores. The four apical and the four basal pores are elliptical and far larger than the four dorsal and the four ventral pores. Eesembles a Dictyospyris with open lateral gates.
Dimensions. — Height of the sagittal ring 0'08, breadth 0'06.
Habitat. — Central Pacific, Station 272, depth 2600 fathoms.
6. Clathrocircus multiforis, n. sp. (PI. 92, fig. 10).
Sagittal ring circular, smooth, with ten to twelve pairs of roundish pores, forming together a complete lattice-girdle with two parallel circular rows of pores. Four larger of these are the four gates of the basal ring (two jugular and two cardinal pores).
Dimensions. — Diameter of the ring O'l to 015, breadth 0'03 to 0'05.
Habitat.— Central Pacific, Stations 263 to 274, depth 2350 to 2925 fathoms.
Subfamily 2. CORTINISCIDA, Haeckel.
Definition. — S emantida with large, typical, regularly disposed basal feet (originally three cortinar feet, one odd caudal and two paired pectoral).
Genus 411. Cortiniscus,1 n. gen.
Definition. — S emantida with three typical basal feet (an odd caudal foot and two paired lateral or pectoral feet).
The genus Cortiniscus is of peculiar importance, as the common ancestral form of the Cortiniscida, or those Semantida in which the basal ring is provided with typical, regularly disposed basal feet — three, four, or six. Since these typical basal feet (or " cortinar feet ") are preserved in the greater number of all NASSELLARIA, determining their triradial structure, they possess a great morphological value. Cortiniscus exhibits the same three primary feet as Cortina, from which it differs in the production of two or more basal pores (between the odd caudal and the paired lateral feet).
1. Cortiniscus tripodiscus, n. sp. (PI. 92, fig. 11).
Sagittal ring ovate, thorny, with three prominent, distorted edges ; its dorsal rod nearly straight and vertical, with one or two pairs of short thorns ; its ventral rod strongly curved, with three or four pairs of divergent thorns. Basal ring larger than the sagittal ring, with two semicircular gates and obliquely ascending halves, which on the inner and lower edge are smooth,
1 Cortiniscus= Small cortina or tripod.
964 THE VOYAGE OF H.M.S. CHALLENGER.
on the outer and upper thorny. Apical horn and the three divergent feet nearly equal, straight, about as long as the sagittal ring, with three thorny edges.
Dimensions. — Height of the sagittal ring 01 to 012, breadth 0'07 to 0'09.
Habitat. — Central Pacific, Stations 270 to 274, depth 2350 to 2925 fathoms.
2. Cortiniscus dipylaris, n. sp. (PL 92, fig. 13).
Sagittal ring nearly semicircular, with prominent distorted edges and six pairs of small roundish papillate tubercles (three pairs on the straight dorsal, three on the curved ventral rod). Apical horn short and stout, with a tuberculate knob. Basal ring smaller than the sagittal ring with two elliptical gates. Three feet short and stout, irregularly branched like a cauliflower, with numerous short papillate tubercles.
Dimensions. — Height of the sagittal ring Oil, breadth 0'08.
Habitat. — Central Pacific, Station 268, depth 2900 fathoms.
3. Cortiniscus tripylaris, n. sp.
Sagittal ring elliptical, smooth. Apical horn conical, smooth. Basal ring larger than the sagittal ring, with three elliptical gates of equal size ; two paired, posterior (jugular pores) between the basal parts of the caudal foot and the two pectoral feet), and an odd, anterior (sternal pore) between the basal parts of the two pectoral feet and a connecting horizontal convex sternal bow.
Dimensions. — Height of the sagittal ring 0'09, breadth 0'06.
Habitat. — Tropical Atlantic, Station 348, depth 2450 fathoms.
4. Cortiniscus tetrapylaris, n. sp.
Sagittal ring elliptical, with four pairs of short branched thorns, two posterior on the straight dorsal, and two anterior on the curved ventral rod. Basal ring smaller than the sagittal ring, with four triangular gates ; the two anterior (jugular pores) a little smaller than the two posterior (cardinal pores). Apical horn and the three divergent feet shorter than the sagittal ring, irregularly branched, with curved, often tuberculate branches.
Dimensions. — Height of the sagittal ring 0'08 to 0'012, breadth 0'06 to 01.
Habitat. — Fossil in Barbados.
5. Cortiniscus typicus, n. sp. (PI. 92, fig. 12).
Sagittal ring ovate, thorny, with three distorted edges ; dorsal rod nearly straight and vertical prolonged upwards into a stout thorny apical horn, downwards into the caudal foot. Basal ring smaller than the sagittal ring, with four elliptical or nearly triangular gates ; the two anterior (jugular pores) about half as large as the two posterior (cardinal pores). Three feet of equal size, thorny, divergent, straight or slightly curved, about as long as the diameter of the sagittal ring.
Dimensions. — Height of the sagittal ring 014 to 018, breadth 01 to 012.
Habitat. — Cosmopolitan ; Atlantic, Indian, Pacific, at various depths.
REPORT ON THE RADIOLARIA. 965
Genus 412. Stephaniscus,1 n. gen.
Definition. — S emantida with four typical basal feet (two sagittal and two lateral or pectoral feet).
The genus Stephaniscus differs from the preceding Cortiniscus in the production of a fourth (sternal) foot, and therefore exhibits the same relation to it that Stephanium among the Stephanida bears to Cortina. It differs from Stephanium in the pro- duction of a basal ring, with pores or gates between the bases of the basal feet. Two of these feet are sagittal (the posterior caudal and the anterior sternal foot), whilst the other two are lateral or pectoral (right and left). The basal lattice-plate exhibits either two pores (" jugular gates ") or four pores (two anterior jugular and two posterior cardinal gates).
1. Stephaniscus tetrapodius, n. sp.
Sagittal ring nearly circular, smooth, with a short conical apical horn. Basal ring square, smooth, with two triangular gates. Four feet simple, equal, conical, divergent, about as long as the diameter of the ring.
Dimensions. — Height of the sagittal ring 0-08, breadth 0'07.
Habitat. — Central Pacific, Stations 270 to 274, depth 2350 to 2925 fathoms.
2. Stephaniscus quadrifurcus, n. sp. (PI. 92, fig. 14).
Sagittal ring subcircular, thorny, with a small thorny apical horn. Basal ring also nearly circular, with two large semicircular gates and a few small thorns. All four feet curved and forked, the fork-branches again ramified, with numerous short curved and pointed branches. The two lateral feet (right and left) are larger and more branched than the two sagittal feet (sternal and caudal foot).
Dimensions. — Height of the sagittal ring 0'12, breadth O'l.
Habitat. — Central Pacific, Station 266,. depth 2750 fathoms.
3. Stephaniscus quadrigatus, n. sp. (PI. 92, fig. 15).
Sagittal ring oblique, ovate, with three prominent thorny edges ; its dorsal rod nearly straight and vertical, the ventral rod strongly curved ; apex with a small curved horn. Basal ring with a few short thorns and four gates of different size ; the two anterior (jugular pores) ovate or nearly triangular, two-thirds as broad as the two posterior subcircular or pentagonal (cardinal pores). All
1 Stephaniscus = Small coronet or garland; oTHp
966 THE VOYAGE OF H.M.S. CHALLENGER.
four feet simple, curved, with three edges, the posterior (caudal) foot larger, the anterior (sternal) foot smaller than the two lateral (pectoral) feet.
Dimensions. — Height of the sagittal ring 0'09, breadth 0'07.
Habitat. — Tropical Atlantic, Station 351, surface.
4. Stephaniscus medusinus, n. sp.
Sagittal ring elliptical, thorny, with a larger apical horn. Basal ring nearly square, with short marginal thorns and four large ovate gates of nearly equal size. All four feet of equal size divergent, curved, irregularly branched, with short curved branches.
Dimensions. — Height of the sagittal ring 013, breadth 0'09.
Habitat. — South Atlantic, Station 332, depth 2200 fathoms.
Genus 413. Semantiscus,1 n. gen.
Definition. — S emantida with six typical basal feet (two sagittal, two pectoral, and two tergal feet).
The genus Semantiscus may be the archetype of those NASSELLARIA which exhibit six typical basal feet, in combination with the sagittal ring. Three of these are the primary feet of Cortina and Cortiniscus, the other three are secondary productions between the former. The basal ring may possess either two, four, or six basal pores.
1. Semantiscus hexapodius, n. sp. (PI. 92, fig. 16).
Sagittal ring elliptical, with a large branched apical horn. Basal ring small, square, with two small triangular gates (or jugular pores). Prom its periphery there arise six short and stout cylindrical feet, one very large (caudal) from the posterior corner, two tergal on each side, two opposite (pectoral) from the kteral corners, and one odd sternal from the anterior corner. All six spines bear a bunch of ten to twenty stout pointed conical branches, partly simple, partly forked.
Dimensions. — Height of the sagittal ring 0'12, breadth 0'08.
Habitat. — Central Pacific, Station 266, depth 2750 fathoms.
2. Semantiscus hexaspyris, n. sp. (PI. 92, fig. 18).
Sagittal ring semicircular, broad, latticed, with two pairs of irregular dorsal and two pairs of ventral pores. The dorsal rod is straight and vertical, prolonged upwards into a short serrate apical horn, downwards into a straight linear caudal foot. The ventral rod is curved and prolonged into a similar sternal foot. Basal ring hexagonal, with four ovate gates (two smaller jugular and two larger cardinal pores); its four lateral corners prolonged into four curved thorny lateral feet (two
1 Semantiscus = Small signet-ring
REPORT ON THE RADIOLARIA. 967
anterior larger pectoral, and two posterior smaller tergal feet). This species may be regarded as a commencing Hexaspyris or Lirwspyris.
Dimensions. — Height of the sagittal ring O08, breadth 0'06.
Habitat. — Central Pacific, Station 271, depth 2425 fathoms.
3. Semantiscus hexapylus, n. sp. (PI. 92, fig. 17).
Sagittal ring ovate, thorny, with a small apical horn. Basal ring with six roundish or nearly triangular gates; the -two jugular pores are smaller than the two cardinal and larger than the two cervical pores. The separating bars between these six pores are prolonged into six straight, thorny widely divergent feet ; three larger feet (the caudal and the two pectoral) with a pair of apophyses three smaller between them simple (the sternal and the two tergal feet).
Dimensions. — Height of the sagittal ring 0'13, breadth 0'09.
Habitat. — "Western Tropical Pacific, Station 225, depth 4475 fathoms.
Family L. CORONIDA, Haeckel.
Triostephida, Haeckel, 1881, Prodromus, p. 445.
Definition. — S tephoidea with two crossed vertical rings, perpendicular one to the other (the primary sagittal and the secondary frontal ring). Usually their common base bears a horizontal basal ring, but a mitral ring (or a horizontal ring at the apex) is never developed.
The family Coronida comprises those Stephoidea in which the primary sagittal ring (of the Stephanida and Semantida) becomes crossed by a second vertical ring, the lateral or frontal ring. Between these two vertical meridian rings, perpen- dicular to one another, four large apertures remain constantly open, the " lateral " gates. But besides these four constant openings, usually (excepting only in the Zygo- stephanida) other gates are developed on the common base of the two crossed rings, produced by a third, horizontal, basal ring. These basal gates are the same which we have found already in the Semantida.
The distinction of the Coronida from the other Stephoidea is always easy. In the Stephanida and Semantida, the frontal ring, or the second meridian ring, which we find in all Coronida, is never developed. On the other hand these latter never exhibit the typical "mitral ring," or the second, upper, horizontal ring, which distinguishes the Tympanida.
We distinguish here, among the Coronida, four different subfamilies, which perhaps afterwards may be better separated as families. Of these four groups the Zygo- stephanida and Acanthodesmida exhibit the nearest relationship to the Stephanida, whilst the Eucoronida and Trissocyclida possess a closer affinity with the Semantida.
968 THE VOYAGE OF H.M.S. CHALLENGER.
The Zygostephanida, constituting the first subfamily, exhibit four large gates only, and differ from all other Coronida in the absence of a basal ring and of basal gates. Therefore the skeleton is entirely composed of two crossed vertical rings, perpendicular to one another ; the first is the primary or sagittal ring (inherited from the Stephanida), the second is the new lateral or frontal ring. The four large lateral gates are either quite simple (Zygostephanus) or partly closed by loose and irregular lattice-work (Zygo- stephanium). The Zygostephanida may be derived directly from the Stephanida by development of lateral branches forming a frontal ring. They commonly possess the same characteristic spines or branches, and the same typical difference between the straight dorsal rod and convex ventral rod of the sagittal ring, which we found in the greater number of Stephanida. The frontal ring is commonly elliptical or kidney-shaped, and much larger than the ovate sagittal ring.
The Acanthodesmida, forming the second subfamily of Coronida, differ from all other members of this family in the possession of a large simple basal gate, surrounded by a simple horizontal basal ring. Only this ring is complete, whilst the two crossed vertical meridian rings (the primary sagittal and the secondary frontal ring) are incomplete, both truncated at the base by the basal ring. Therefore there remain here between the three rings five large gates (recognised previously by Johannes Miiller in 1856 mAcantho- desmid) : four lateral gates (the same as in the Zygostephanida) and one central basal gate. The latter is always quite simple, and serves for the emission of the pseudo- 'podia, arising from the basal pole of the central capsule. The four lateral gates are either quite simple (Coronidium) or partly closed by irregular loose lattice-work (Acanthodesmia). The subfamily Acanthodesmida may be derived either directly from the Stephanida (by development of a central basal gate) or from the Eucoronida (by loss of the basilar part of the sagittal ring).
The Eucoronida, the third subfamily, are the most important group of the Coronida ; their numerous species are much more frequent and more widely distributed than those of the other three subfamilies. They may be derived immediately from, the Semautida by the development of a lateral or frontal ring. This remains incomplete in the basal part, whilst the two other rings, perpendicular to it (the vertical sagittal ring and the horizontal basal ring), are complete. Therefore the shell constantly exhibits six large open gates between the three rings ; four lateral gates (the same as in the Zygo- stephanida and Acanthodesmida) and two basal gates (inherited from Semantis) ; the latter correspond to the " jugular pores " of the Spyroidea and Cyrtoidea; they remain constantly simple. The four lateral gates may also remain simple (Eucoronis) or they may become partly closed by irregular loose lattice-work (Plectocoronis) . The remarkable genus Podocoronis is distinguished by the development of typical descending basal feet, which are regularly disposed and correspond to the typical " cortinar feet " of the other NASSELLAEIA. There may be developed either two lateral feet (as lower
REPORT ON THE RADIOLARIA. 969
prolongations of the segments of the frontal ring), or three feet (one caudal and two pectoral, as in Cortina and Cortiniscus), or four feet (two sagittal and two lateral, as in Stephanium and Stephaniscus), or six feet (two sagittal, two pectoral, two tergal, as in Semantiscus), sometimes numerous feet (as in Petalospyris and Anthocyrtis, &c.).
The Trissocyclida represent the fourth and last subfamily of Coronida, distinguished from all others in the possession of three complete rings, perpendicular one to another, and of eight large gates separated by them. Two of the three rings are vertical (the primary sagittal and the secondary frontal ring), the third is horizontal (the basal ring). The four upper gates correspond to the four lateral gates of the preceding three subfamilies ; the four lower gates are the same as the four basal gates of Semantrum (two primary jugular and two secondary cardinal gates) ; therefore the Trissocyclida may be derived directly from these Semantida by development of a complete frontal ring. Probably the two jugular gates were . originally smaller than the two cardinal, but usually they have become equal. In Tristephanium (the common ancestral form of the Trissocyclida) and in the closely allied Tricyclidium the four basal gates remain smaller than the four lateral gates. But in two other genera, Trissocircus and Trissocyclus, the four lower or basal gates reach the same size as the four upper or lateral gates ; therefore all eight gates become equal and the basal ring becomes equatorial. In the most regular species of the latter genera also the three rings become perfectly equal and cannot be any longer distinguished. Here the original bilateral (or dipleuric) funda- mental form of the shell passes over into a regular cubic, or octahedral form (with three equal, isopolar axes, perpendicular one to another). The eight large gates of the Trissocyclida usually remain simple (Tristephanium, Trissocircus), but sometimes they become partly closed by loose lattice-work (Tricyclidium, Trissocyclus).
The original rings, and the secondary rods or bars, composing the loose framework of the Ooronida are either roundish (with circular or elliptical transverse section) or three-edged (with triangular transverse section), rarely quadrangular or provided with distorted edges. The branches or spines arising from them, are either simple or branched, and offer a great variety in number, form, and disposition. The most important forms are those which develop the three typical basal feet of Cortina, e.g., Podocoronis cortina (PI. 97, fig. 2).
The Central Capsule of the Coronida is the same as in the other Stephoidea (comp. p. 937), and offers all those characteristic peculiarities of "Monopylea" which we have mentioned above in the general description of the NASSELLARIA (p. 890). Usually it is spherical or ellipsoidal, often violin-shaped or bilobed, with a sagittal constriction. The porochora of its basal pole is in close contact with the base of the sagittal ring.
(ZOOL. CHALL. EXP. — PART XL. 1886.) Rr.122
970
THE VOYAGE OF H.M.S. CHALLENGER.
I. Subfamily
Zygostephanida. Four lateral gates (no basal gate).
II. Subfamily
Acanthodesmida. Five large gates (four lateral and one simple basal).
III. Subfamily
Eucoronida.
Six large gates (four lateral and two basal).
IV. Subfamily
Trissocyclida. Eight large gates (four -
upper lateral and four
lower basal).
Synopsis of the Genera of Coronida.
Two meridional rings ~|
S^^l*-^ gates simple, dicular to one f ,-, , ,
another (no basal | Four lateral 8ates Partly latticed' ring). J
Two meridional rings ")
(sagittal and frontal) \ v , . ,
incomplete, both I Four lateral 8ates 8lmPle'
truncated by the [ -, , .
complete horizontal | Four lateral Sates Partly latticed'
basal ring. J
Two rings (the sagittal meridional ring and the horizontal basal ring) complete, the frontal meridian ring incomplete.
Two meridional rings (sagittal and frontal) and the horizontal basal ring complete. - All three complete rings perpendicular to one another.
Basal ring f Gates simple, . without larger I descending 1 Gates partly lat- feet. [ ticed,
Basal ring with large, regularly disposed, descending feet. Gates simple,
414. Zygostephamis.
415. Zygostephanium.
416. Coronidium.
417. Acantkodesmia.
418. Eucoronis.
419. Plectocoronis.
420. Podocoronis.
Four upper gates larger
than the four lower.
Gates simple, . 421. Tristephanium.
Gates partly lat- ticed,
{Gates simple, . Gates partly lat- ticed,
422. Tricydidium.
423. Trissoeir/MS.
424. Trissocydus.
Subfamily 1. ZYGOSTEPHANIDA, Haeckel, 1881, Prodromus, p. 446.
Definition. — C o r o n i d a with four large lateral gates, without basal gate. Skeleton composed of two complete vertical rings, perpendicular one to another — the primary sagittal and the secondary frontal ring.
Genus 414. Zygostephanus,1 Haeckel, 1862, Monogr. d. Eadiol, p. 268.
Definition. — C o r o n i d a with four large, simple, lateral gates, without basal gate and lattice-work. Skeleton composed of two simple meridional rings, perpendicular to one another.
The genus Zygostephanus, founded by me in 1862 for the Mediterranean Zygoste- phanus mulleri, is the simplest and most primitive of all the Coronida, and may there-
1 Zygostephamis — Yoked ring ; £vyov,
REPORT ON THE RADIOLARIA. 971
fore be regarded as the common ancestral form of this family. The simple skeleton is composed of two meridional rings only, perpendicular one to another — a sagittal and a frontal ring.
Subgenus 1. Zygostephus, Haeckel, 1881, Prodromus, p. 446.
Definition. — The two vertical rings of nearly equal height, therefore without sagittal constriction.
1. Zygostephanus dissocircus, n. sp. (PI. 93, fig. 1).
Both rings elliptical, of nearly equal height, smooth, without spines. Frontal ring somewhat longer than the sagittal. No sagittal constriction.
Dimensions. — Height of the rings 0'07, breadth O'l.
Habitat. — Cosmopolitan; Mediterranean, Atlantic, Pacific, surface.
2. Zygostephanus serratus, n. sp.
Both rings elliptical, of nearly equal height, with a serrate prominent edge on the outer convexity (in the transverse section three-edged). No sagittal constriction. Dimensions. — Height of the rings 0'08, breadth 012. Habitat. — Central Pacific, Station 266, depth 2750 fathoms.
3. Zygostephanus miilleri, Haeekel.
Zygostephanus miilleri, Haeckel, 1862, Monogr. d. Radiol., p. 268, Taf. xii. fig. 2.
Both rings elliptical, of nearly equal height, armed with numerous (about fifty) slender curved spines, as long as the radius of the rings ; commonly each ring with twelve pairs of divergent spines. No sagittal constriction.
Dimensions. — Height of the rings 0'06, breadth O'l.
Habitat. — Mediterranean (Messina), surface.
4. Zygostephanus ratnosus, n. sp.
Both rings elliptical, of nearly equal height, armed with numerous branched spines, which are arranged on each ring in two divergent rows ; the branches of the spines are curved and partly protect the open gates. No sagittal constriction.
Dimensions. — Height of the rings 0'07, breadth 0'09.
Habitat. — North Pacific, Station 244, depth 2900 fathoms.
972 THE VOYAGE OF H.M.S. CHALLENGER.
Subgenus 2. Zygostephaniscus, Haeckel, 1881, Prodromus, p. 446.
Definition. — The two vertical rings of different heights; the frontal ring higher than the sagittal ring, therefore with a sagittal constriction in the median plane.
5. Zygostephanus reniformis, n. sp.
Frontal ring kidney-shaped, in the upper half convex, in the lower half concave, in the latter with a deep sagittal constriction, armed with numerous irregular short spines. Sagittal ring thicker and lower, only two-thirds as high, with four pairs of short divergent spines (two ventral and two dorsal pairs).
Dimensions. — Height of the frontal ring 013, hreadth 0'2.
Habitat. — Central Pacific, Station 271, depth 2425 fathoms.
6. Zygostephanus violina, n. sp.
Frontal ring violin-shaped, on the upper and the lower margin concave, with a deep sagittal constriction, armed with numerous irregular spines, which are partly simple, partly branched. Sagittal ring thicker and lower, only half as high, with a few short conical spines at the apical and hasal poles.
Dimensions. — Height of the frontal ring 012, breadth 018.
Habitat. — South Atlantic, Station 332, depth 2200 fathoms.
7. Zygostephanus bicornis, n. sp. (PI. 93, fig. 2).
Frontal ring violin-shaped, on the upper and the lower margin concave, with a deep sagittal con- striction ; its two halves pentagonal. Between numerous smaller spines there arise from the frontal ring six groups of larger branched spines, two odd in the corners of the highest points (curved like two horns), two branched pairs on the prominent lateral corners (at right and left), and two pairs in the corners of the lowest points (like four branched basal feet). Sagittal ring only two-thirds as high, with four pairs of irregular spines.
Dimensions. — Height of the frontal ring Oil, breadth 016.
Habitat. — South Pacific, Station 300, depth 1375 fathoms.
Genus 415. Zygostephanium,1 Haeckel, 1881, Prodromus, p. 446.
Definition. — C o r o n i d a with four large, partly latticed, lateral gates, without basal gate. Skeleton composed of two meridional rings perpendicular to each other.
The genus Zygostephanium differs from the preceding ancestral genus Zygostephanus in the development of lattice-work along the two crossed rings, produced by their anasto- mosing branches. Therefore the four large lateral gates between them, which are quite simple, in the preceding genus here become more or less fenestrated.
1 Zygostephanium = Small yoked ring ; £vyoi>,
REPORT ON THE RADIOLARIA. 973
i
1. Zygostephanium dizonium, n. sp. (PI. 93, fig. 3).
Tympaniscus dizonius, Haeckel, 1882, Manuscript
Both rings elliptical, of nearly equal height, smooth, without spines. Sagittal ring with four pairs of small pores (two apical pairs and two basal pairs). Frontal ring with three pairs of small pores (one pair lateral, one pair above and one pair below).
Dimensions. — Height of the frontal ring 0'08, breadth 012.
Habitat. — Central Pacific, Station 263, depth 2900 fathoms.
2. Zygostephanium paradictyum, n. sp. (PI. 93, fig. 4).
Frontal ring kidney-shaped, in the upper half convex, in the lower concave, in the latter with a deep sagittal constriction. Sagittal ring ovate, ubout two-thirds as high as the frontal ring. Both rings three-edged, armed with numerous short and branched bristle-shaped spines, which anasto- mose along their three edges and produce two series of irregular polygonal pores.
Dimensions. — Height of the frontal ring 0'08, breadth 0'13.
Habitat. — North Pacific, Station 236, surface.
3. Zygostephanium constrictum, n. sp.
Frontal ring violin-shaped, concave on the upper and lower margins, with a deep sagittal constriction. Sagittal ring ovate, about two-thirds as high as the frontal ring. Both rings covered with numerous branched irregular spines, which partly anastomose along the edges of the rings, and produce small irregular polygonal pores.
Dimensions. — Height of the frontal ring 012, breadth 018,
Habitat. — Central Pacific, Station 272, depth 2600 fathoms.
Subfamily 2. ACANTHODESMIDA, Haeckel, 1881, Prodromus, p. 445.
Definition. — C o r o n i d a with five large gates (four lateral and one basal). Skeleton composed of three rings, perpendicular one to another, two of which are vertical and incomplete (the primary or lateral, and the secondary or frontal), the third is horizontal and complete (the tertiary or basal ring).
Genus 416. Coronidium,1 Haeckel, 1881, Prodromus, p. 445.
Definition. — C o r o n i d a with five large simple gates (four lateral and one basal). Skeleton composed of two incomplete meridional rings and one complete basal ring, without lattice-work.
1 Coronidium = Small crown ;
974 THE VOYAGE OP H.M.S. CHALLENGES.
The genus Coronidium and the following, nearly allied Acanthodesmia, form together the peculiar subfamily of Acanthodesmida — not in the wider sense in which I first founded this group (1862, Monogr. d. Kadiol., p. 265), but in the restricted sense, which is exactly defined in my Prodromus (1881, p. 445). According to this definition, the shell is composed of three different rings, perpendicular to one another ; only one of these is complete, the simple horizontal basal ring ; the two others are incomplete and vertical (the primary or sagittal and the secondary or frontal ring). Therefore there remain constantly between the three rings five characteristic large openings or gates ; four of these are lateral (between the halves of the two meridional rings), the fifth is basal, enclosed by the horizontal bas