Legion III. NASSELLARIA, (continued 4)

The genus Circotympanum comprises those Tympanida in which two simple horizontal rings of different size (an upper smaller "mitral ring," and a lower larger "basal ring") are connected by a variable number of divergent rods or columellæ (at least six or eight). Circotympanum is probably derived from Tympaniscus or Tympanidium by partial reduction of the sagittal ring, the upper (apical) and lower (basal) part of which is lost. The geometrical fundamental form is a truncated pyramid with six to eight or more edges.

1. Circotympanum hexagonium, n. sp.

Mitral and basal ring hexagonal, the latter twice as broad as the former, each with a simple small spine on the six corners. Six columellæ nearly straight, as long as the radius of the basal ring. All rods with three prominent edges.

Dimensions.—Breadth of the mitral ring 0.06, of the basal ring 0.11.

Habitat.—Central Pacific, Station 268, depth 2900 fathoms.

2. Circotympanum octogonium, n. sp. (Pl. 94, fig. 17).

Mitral and basal rings octagonal, the latter one and a half times as broad as the former. Eight columellæ slightly curved, thorny. The mitral ring bears on each corner a short ascending spine, the basal ring a larger, thorny, obliquely descending spine, which has some recurved thorns on the upper edge. All rods more or less thorny.

Dimensions.—Breadth of the mitral ring 0.06, of the basal ring 0.09.

Habitat.—Central Pacific, Station 271, depth 2425 fathoms.

3. Circotympanum decagonium, n. sp.

Mitral and basal rings circular, the latter nearly twice as broad as the former, both armed with scattered irregular thorns. Ten columellæ smooth, curved.

Dimensions.—Breadth of the mitral ring 0.07, of the basal ring 0.12.

Habitat.—North Pacific, Station 244, depth 2900 fathoms.

Genus 440. Eutympanium,^[58] Haeckel, 1881, Prodromus, p. 447.

Definition.—Tympanida with two simple equal horizontal rings, connected by numerous (six to eight or more) parallel and vertical columellæ.

The genus Eutympanium contains those Tympanida in which the drum-shaped shell is composed of two simple, parallel and equal horizontal rings, and numerous vertical and parallel rods or columellæ connecting them. The number of the latter is at least six or eight. Two opposite of these must be regarded as remaining vertical parts of the sagittal ring, two others as parts of the frontal ring, whilst the other columellæ (between the former and the latter) are secondary and intercalated. Therefore Eutympanium may be derived from Tympanidium by reduction and loss of the apical and basal parts of the sagittal ring.

1. Eutympanium musicantum, n. sp. (Pl. 83, fig. 2).

Eight parallel and vertical columellæ, simple, straight and smooth. Both horizontal rings equal, circular, each armed with eight to twelve short conical thorns.

Dimensions.—Height of the shell 0.09, breadth 0.07.

Habitat.—Central Pacific, Station 266, depth 2750 fathoms.

2. Eutympanium octonarium, n. sp.

Eight vertical columellæ slightly curved, thorny. Both horizontal rings equal, octagonal, each armed with eight large, irregularly-branched spines, which on the mitral ring are directed obliquely upwards, on the basal ring downwards.

Dimensions.—Height of the shell 0.12, breadth 0.1.

Habitat.—Central Pacific, Station 268, depth 2900 fathoms.

3. Eutympanium coronarium, n. sp.

Eight thorny columellæ, obliquely descending and curved like a bow, divergent in the upper part, convergent in the lower. Basal ring circular, mitral ring octagonal. Both horizontal rings armed with eight stout thorny spines, which on the mitral ring are smaller and directed obliquely upwards, on the basal ring larger and directed downwards, each with a recurved hook.

Dimensions.—Height of the shell 0.08, breadth 0.06.

Habitat.—South Atlantic, Station 332, depth 2200 fathoms.

4. Eutympanium militare, n. sp. (Pl. 82, fig. 11).

Ten parallel and vertical columellæ straight and smooth, cylindrical. Both horizontal rings equal, circular, armed with numerous short conical spines, divergent in all directions. Ten to twenty spines on each ring larger than the others.

Dimensions.—Height of the shell 0.1, breadth, 0.08.

Habitat.—Western Tropical Pacific, Station 225, depth 4475 fathoms.

5. Eutympanium dodecarium, n. sp.

Twelve vertical columellæ, slightly curved, smooth. Mitral and basal rings circular, both horizontal rings armed with twelve stout, irregularly-branched spines, which are prolongations of the columellæ, and on the mitral ring directed upwards, on the basal ring downwards.

Dimensions.—Height of the shell 0.13, breadth 0.1.

Habitat.—South Pacific, Station 300, depth 1375 fathoms.

Order VI. CYRTELLARIA, Haeckel, 1881.

Definition.—Nassellaria with a complete lattice-shell enveloping the central capsule.

Suborder I. SPYROIDEA, Haeckel.

Definition.—Nassellaria with a complete lattice-shell, exhibiting constantly a bilocular cephalis with a sagittal constriction.

The suborder Spyroidea, and the two following closely allied suborders, Botryodea and Cyrtoidea, represent together that large group of Radiolaria which I first described in my Monograph (1862, pp. 272, 280) as the family Cyrtida, but afterwards as a separate order (or sublegion) under the name Cyrtellaria (1883, Jena. Sitzungsber., Feb. 16, p. 18). This group comprises all those Monopylea or Nassellaria which possess a complete lattice-shell, whilst the preceding Plectellaria never develop a perfect fenestrated shell enveloping the central capsule. The Spyroidea differ from the other Cyrtellaria (Botryodea and Cyrtoidea) in the bilocular shape of the cephalis, which is bisected by the sagittal ring and a corresponding longitudinal constriction into two symmetrical halves.

The Spyroidea appear in the first system of Polycystina of Ehrenberg (1847, loc. cit., pp. 53, 54) as the fourth of his seven families, under the name Spyridina, with the following definition:—"Testæ nucleo destitutæ (associatæ et coalitæ); cellulæ binæ clathratæ, nucis forma amplæ, strictura longitudinali levius discretæ." Ehrenberg united them with his "Polycystina composita or Spumellaria" and separated them from the closely allied "Polycystina solitaria or Nassellaria." He distinguished among them five genera, two of which have no external appendages (Dictyospyris and Pleurospyris), whilst the other three possess spiny or lamellar appendages (Ceratospyris, Cladospyris, and Petalospyris). These five genera and the accompanying definitions were also repeated in the same terms in the last system of Ehrenberg (1875, loc. cit., p. 157). In my Monograph (1862, pp. 280, 291) the Spyroidea are enumerated as a subfamily of the Cyrtida, under the name Zygocyrtida, with the following definition:—"Lattice-shell divided by an annular sagittal longitudinal constriction into two neighbouring equal joints or chambers." I adopted at that time the above five genera of Ehrenberg, only eight species of which were known.

Richard Hertwig gave in 1879 the first accurate description of the central capsule of the Spyroidea, and demonstrated that they possess the same characteristic structure of the capsule, with a porochora and a podoconus, that is common to all Monopylea. He separated the Zygocyrtida from the other Cyrtida, and united them with the Stephoidea (Lithocircus) in the family Acanthodesmida. In my Prodromus (1881, p. 449) I adopted that division and put the "Spyrida or Spyroidea" as a separate family between the Cyrtoidea and Stephoidea. I there gave the following definition:—"Monopylaria gemina, testa silicea clathrata gemina, cameris binis juxta compositis, annulo verticali sagittali contiguis, capsula centrali a testa inclusa. Promorpha dipleura vel bilaterali, dextro et sinistro antimero symmetricis, plano sagittali annuloque separatis. Polum superiorem axis verticalis vel principalis plerumque spina apicalis (vel occipitalis) occupat, polum inferiorem ostium clathratum (poris tribus aut quatuor aut pluribus) et spina caudalis (posterior). Ad dextram et sinistram duæ spinæ laterales distant. Ab hac forma tripoda (Monocyrtida triradiata acuta cum annulo mediano) diversæ Spyridum formæ derivandæ sunt." I there divided the Spyrida into seven subfamilies and forty-eight genera. Bütschli in 1882 published accurate researches on the Zygocyrtida in his Beiträge zur Kenntniss der Radiolarien-Skelete, insbesondere der der Cyrtida (Zeitschr. f. wiss. Zool., vol. xxxvi. p. 501, Taf. xxxii.). He gave a very exact anatomical description of the skeleton of several fossil Spyroidea of Barbados, and pointed out their close affinity to the Acanthodesmida on the one hand, and to the Cyrtida on the other. Regarding their phylogenetical relation, he supposed that the Zygocyrtida have descended from the Acanthodesmida (our Stephoidea) and are the ancestors of all other Cyrtida. The best part of this valuable paper of Bütschli is his exact description of the sagittal ring and its apophyses, producing the basal plate; and the general conception thus derived of the essential parts of the skeleton in all Monopylea, bearing a sagittal ring. But his general conclusions were partly erroneous, since the fossil Spyroidea and Cyrtoidea of Barbados, upon which they were founded, contain only the minority of genera of the large group; and many important and typical forms remained unknown to him.

The numerous new genera discovered in the rich collection of the Challenger, and mainly in the wonderful Radiolarian ooze of the Central Pacific (Stations 263 to 274) throw a new light upon the complicated affinities of the whole group, and manifest a far greater richness in developmental variations and admirable morphological productions than Bütschli could suppose. The following description, however, must remain very incomplete, since the exact and thorough study of all individual forms, in the same manner as Bütschli had done in the case of a small number of species, would require several years. I can therefore only give the basis of further researches.

In the majority of Spyroidea the three essential elements of the Nassellarian skeleton are easily recognisable, viz.:—A, the vertical sagittal ring of the Stephoidea; B, the basal tripod of the Plectoidea, and C, the latticed cephalis of the Cyrtellaria. These three elements are constantly so combined that the primary sagittal ring bisects the cavity of the lattice-shell and produces an external, longitudinal, more or less distinct constriction, separating the lateral inflated halves of the bilocular cephalis; while the three divergent feet of the basal tripod descend from the cortinar or basal plate of the cephalis. The number of the feet is often augmented; they are rarely wanting (probably reduced). The sagittal ring is constantly present, though its relation to the shell-wall exhibits many modifications. The bilocular form of the fenestrated cephalis, with its sagittal constriction, is characteristic of all true Spyroidea, and separates them from the Botryodea (with multilobate cephalis) on the one hand, and from the Cyrtoidea (with simple cephalis) on the other. There are, however, some intermediate forms between these three suborders of Cyrtellaria, which show a direct transition to one another. Almost constantly the length of the three dimensive axes in the cephalis of the Spyroidea is so different that the lateral or frontal axis is the longest, the sagittal or dorso-ventral axis the shortest, and the principal or longitudinal axis intermediate between them. As in all dipleuric or bilaterally symmetrical forms, the two poles of the frontal axis are equal, whilst the two poles of the sagittal and of the principal axis are more or less different. In only a few forms of Spyroidea these differences are difficult to make out; usually the dorsal side is distinctly different from the ventral, and the apical side from the basal. A perfect knowledge of the dipleuric shell requires therefore accurate observation from all six sides.

The suborder of Spyroidea is here divided into four different families. In the first and original family, the Zygospyrida, the shell is represented by the bilocular cephalis only. The second family, Tholospyrida, is distinguished by a fenestrated cupola or galea, a hemispherical or conical dome, arising from the upper or coryphal face of the cephalis. In the third family, Phormospyrida, a thorax is developed, or a fenestrated basal chamber, arising from the lower or basal face of the cephalis. The fourth family, Androspyrida, combines the characters of the second and the third family, a galea arising from the upper and a thorax from the lower face of the cephalis.

The bilocular cephalis, as the most important and constant part of the skeleton in all Spyroidea, requires a further general consideration. Its lattice-work, very variable in the numerous species, is usually more or less different on the six sides of the nut-shaped shell. Its most important part is the horizontal basal plate or lower face, and the sagittal ring arising from it in the vertical median plane. This part of the shell corresponds exactly to the skeleton of the Semantida, and exhibits the same modifications as in that family; it is therefore probable that the majority of the Spyroidea (if not the whole group) have been derived directly from the Semantida by further development of network from the fenestrated ring of Clathrocircus. Whilst in this latter Semantid the two lateral sides of the central capsule remain naked, in the Spyroidea they become enclosed and covered by lattice-work, which arises on the right and left from the ring. In some forms, however, as in the Ceratospyris acuminata of Hertwig, and in my Perispyrida, the frontal ring also of the Coronida and the mitral ring of the Tympanida appear as the initial parts of a complete latticed cephalis.

The basal plate of the cephalis, or the "cortinar plate," the "Basal-Scheibe" of Bütschli, has constantly, according to this author, two pairs of pores, an anterior smaller pair of jugular pores (the pores I of Bütschli) and a posterior larger pair of cardinal pores (the pores II in his description) (compare Pl. 95, figs. 3, 6). This applies to the majority of Spyroidea, but by no means to the whole group. We find basal plates with two pores only (Pl. 95, fig. 1), with three pores (figs. 2, 5), with six pores (figs. 4, 7), with nine pores (Pl. 87, fig. 2), &c. The forms with two basal pores may be derived directly from Semantis (Pl. 92, figs. 1, 2); the common forms with four pores from Semantrum (figs. 3-5); the rarer forms with six pores from Semantidium (figs. 6, 7); and the forms with three pores from Cortiniscus, &c. In this as well as in other respects the variety of different forms and of developmental variations is far greater than Bütschli (1882, loc. cit.) supposed. The bars between the pores of the basal plate possess the same value and the same names as in the Semantida (compare above, p. 954).

The coryphal plate of the cephalis, its upper or apical lattice-plate, does not exhibit such important differences as the opposite basal plate, is far less variable, and is usually pierced by numerous, smaller pores. Some larger pores lie, often in pairs, on the right and left side of the sagittal constriction, and have in some groups a regular form and disposition. Either in the middle of the coryphal plate, or (usually) nearer to its dorsal margin, there arises in majority of Spyroidea an apical horn, directed either vertically or more or less obliquely backwards. In many Spyroidea three horns are developed in the coryphal plate, the odd middle apical horn and two paired frontal or lateral horns arising on each side of the latter and directed more forwards (Pl. 84, figs. 9-12). Sometimes the apical horn disappears, while the two frontal horns remain (Pl. 95, fig. 12).

The anterior or ventral plate of the cephalis (the "Hinterseite" of Bütschli), and the posterior or dorsal side (the "Vorderseite" of that author), exhibit in the majority of Spyroidea more or less marked differences in the number, form, and disposition of their pores, which require a far more accurate description than is here possible. Usually the sagittal constriction of these two plates, produced by the primary vertical ring, is deeper and sharper in the middle of the ventral than in that of the dorsal plate. On both sides of the ring there appear in each plate usually two or three pairs of larger pores, whilst numerous smaller pores are situated towards the lateral sides. We may distinguish the large pores of the ventral plate as facial pores (upper orbital, middle nasal, and lower maxillary pores), and the opposite large pores of the dorsal plate as occipital pores (upper epoccipital, middle mesoccipital, and lower suboccipital pores). A closer comparison of these pores, and of the separating bars in the numerous Spyroidea, may show a regularity of development similar to that offered by the homologies of the parts in the skeleton of the Echinodermata, or of the bones in the skull of the Vertebrata.

The two convex lateral plates of the cephalis, or the right and left sides, both symmetrically equal, do not exhibit the same regularity in the shape, number, and disposition of the pores that the four other sides do. Usually their pores are much smaller and more numerous. In very few forms only a distinct frontal ring is visible (corresponding to that of the Coronida), and in this case the lateral pores are sometimes disposed symmetrically on both sides of this ring. These Spyroidea may have arisen directly from corresponding forms of Coronida.

The sagittal ring (or the primary vertical ring) inherited from the Stephanida and Semantida, shows in the Spyroidea great variety in its form and in its relation to the cephalis. These variations are far greater than Bütschli (1882, loc. cit.) supposed. We may distinguish the following six principal cases:—A. The ring lies completely in the wall of the cephalis, and causes a deep sagittal constriction in it. In this case the lower part or basal segment of the ring separates the basal pores into pairs; its anterior part or ventral rod the facial pores; its upper part or coryphal rod the apical pores; and its posterior part or dorsal rod the occipital pores. No part of the ring is free in the shell-cavity. B. The greater part of the ring lies enclosed in the shell-wall; only its dorsal rod arises free in the shell-cavity and ascends vertically or obliquely to the apex, where it is usually prolonged into the apical horn. This seems to be the most common case. C. The coryphal and the basal part of the ring lie enclosed in the shell-wall, with its dorsal and ventral rod free in the shell-cavity; the dorsal rod ascends vertically to the apex, the ventral rod obliquely upwards to the upper part of the facial plate (the nasal or orbital region). This case, regarded by Bütschli as the usual one, is far less common than he supposed. D. The greater part of the ring lies free in the shell-cavity, its basal rod only is enclosed in the shell-wall, and separates the right from the left group of the cortinar pores. This case seems to be rarer than the preceding. E. The whole ring lies free in the shell-cavity, and is connected with the sagittal constriction of the shell-wall by numerous short radial beams. The distance of the shell-wall from the enclosed ring is usually least on the basal rod, and greatest on the dorsal rod. F. The whole ring lies free in the shell-cavity (as in the preceding case), and is connected by numerous short radial beams with a secondary larger, concentric sagittal ring, which is developed in the longitudinal constriction of the shell-wall.

Comparing these six principal cases, in respect of the relation of the primary sagittal ring to the cephalis of the Spyroidea, we may suppose that they represent together a continuous phylogenetical series of which the first (A) is the original, and the last (F) the latest case; and that the true cause of the various changes is a successive separation of the ring, which becomes more and more free and independent from the lattice-plate of the cephalis. Since the intimate study of the structure of the cephalis in many Spyroidea is very difficult, it requires further accurate observations (from all six sides of the shell). There are also some other more difficult complications of its structure, which cannot be solved without exact study and extended comparison.

Of peculiar importance for the differentiation of the numerous genera of the Spyroidea are the basal feet or the descending and diverging apophyses, which are developed from the base of their cephalis. In general they exhibit the same typical shape which we find in the Plectellaria as well as in the Cyrtoidea, and which we regard therefore as an important common character of the majority of Nassellaria. We may therefore distinguish here also the three primary, and the other ones as secondary feet. The three primary feet, or the "cortinar feet," are the same that we found in the Plagonida and Plectanida, in Cortina and Cortiniscus among the Stephoidea, and in the majority of Cyrtoidea. They also reappear in the same characteristic disposition and connection with the basal plate of the cephalis, in the majority of Spyroidea. The odd caudal foot (c) is the lower prolongation of the dorsal rod of the sagittal ring, which is prolonged upwards into the apical horn. The two paired pectoral feet, however (p′, p′′), are the descending prolongations of the coracal rods (e) which separate the jugular pores (i) from the cardinal pores (k) of the cortinar plate (compare Pl. 95, figs. 2-6).

The three cortinar feet are nearly equally developed in the majority of Spyroidea (compare Pls. 84, 89). But often the odd caudal foot exhibits a different shape from that of the two paired pectoral feet, and in many genera of the group it becomes more or less rudimentary. It has quite disappeared in the subfamily Dipospyrida (Pl. 85); here the two pectoral feet only are developed (often excessively), and are usually opposite in the frontal plane. Such dipodal forms, very common in the Spyroidea, are never found in the Cyrtoidea.

The secondary feet, which we contrast with the three primary feet as later productions, exhibit great variations in number and development. Very frequently three interradial secondary feet become developed, alternating with the three primary cortinar or perradial feet, and opposed to them in pairs (Pl. 95, figs. 7, 8). In these hexapodal Spyroidea (or Hexaspyrida) an odd anterior or sternal foot (z) is opposite to the odd caudal foot, and two paired posterior or tergal feet (t′, t′′) to the two pectoral feet. When the sternal foot becomes rudimentary or lost, pentapodal forms arise (Pentaspyrida, Pl. 95, figs. 9-11), and when the two odd feet (caudal and sternal) disappear, tetrapodal forms arise with two pairs of feet (Therospyrida, Pl. 89, figs. 5, 6). The latter differ from those quadrupedal forms in which two opposite sagittal feet (the caudal and sternal) alternate in the form of a cross with two paired lateral or pectoral feet (Tetraspyrida, Pl. 53, figs. 19, 20). In many Spyroidea the number of basal feet is greatly increased, and they form a regular radial corona around the basal plate, like a circle of tentacles (Polyspyrida, Pl. 87). In this latter case the feet are usually flat and lamellar, whilst in the other groups they exhibit a very variable form, as is seen in Pls. 83-89.

The Central Capsule of the Spyroidea has been accurately observed in only a few genera, and requires a further exact examination regarding the different modifications which occur in their different families. It is very probable that these will agree with the well known modifications in the corresponding groups of Cyrtoidea. The characteristic Monopylean structure of the capsule (with porochora and podoconus) was first described by Richard Hertwig in his Ceratospyris acuminata (loc. cit., p. 72, taf. vii. fig. 2). I found the same afterwards in many other forms. In the Zygospyrida and Tholospyrida the central capsule seems to be usually bilobate (bisected by the sagittal ring), and enclosed in the two chambers of the cephalis. The two lobes of the capsule (right and left) are equal and connected by a smaller middle part, which contains the transverse elliptical nucleus and is enclosed by the sagittal ring; often each lobe contains a large oil-globule. In some forms, however, three or four lobes (sometimes perhaps more) are developed, which pierce the cortinar pores of the basal plate and depend freely between the basal feet (Pl. 53, fig. 19). In the Phormospyrida and Androspyrida the formation of such basal lobes seems to be more frequent; they are here enclosed by the thorax. Usually each lobe contains a large oil-globule. In Nephrospyris (Pl. 90) and in some similar genera the central capsule is violin-shaped, deeply bisected by the sagittal ring; in each of the two lobes a series of oil-vesicles is developed at both poles of the transverse axis (figs. 7, 10); the nucleus, a transverse cylindrical body, is placed in the latter. In the periphery of the voluminous calymma of this singular genus a large number of globular cells are developed (figs. 7, 10), probably symbiotic xanthellæ. In some forms of Nephrospyris these xanthellæ are enclosed by a peculiar inflated girdle, developed in the periphery of the kidney-shaped skeleton (Pl. 90, figs. 1, 4-6).

Synopsis of the Families of Spyroidea.

Shell without thorax; no second shell-joint, developed from the base of the cephalis. Cephalis without galea (or apical cupola), 1. Zygospyrida.

Cephalis with a galea (or apical cupola), 2. Tholospyrida.

Shell with a thorax, or a second shell-joint, developed from the base of the cephalis. Cephalis without galea (or apical cupola), 3. Phormospyrida.

Cephalis with a galea (or apical cupola), 4. Androspyrida.

Shell without thorax; no second shell-joint, developed from the base of the cephalis.

Cephalis without galea (or apical cupola),

1. Zygospyrida.

Cephalis with a galea (or apical cupola),

2. Tholospyrida.

Shell with a thorax, or a second shell-joint, developed from the base of the cephalis.

Cephalis without galea (or apical cupola),

3. Phormospyrida.

Cephalis with a galea (or apical cupola),

4. Androspyrida.

Family LII. Zygospyrida, n. fam. (Pls. 84-87).

Definition.—Spyroidea without galea and thorax; the shell consisting of the bilocular cephalis only and its apophyses.

The family Zygospyrida is by far the richest among the four families of Spyroidea, the number of genera in the whole suborder amounting to forty-five, in the former to twenty-eight; and the number of species in the latter to two hundred and thirty-seven, in the former to one hundred and seventy-two. The number of individuals also found in many species of Zygospyrida is far greater than in any species of the three other families. The shell of the Zygospyrida is represented by the bilocular cephalis only, and never develops a galea (as in the Tholospyrida) nor a thorax (as in the Phormospyrida and Androspyrida). The three latter families have therefore been derived from the former as their common ancestral group.

The Zygospyrida are very similar and nearly related to the Monocyrtida, and in both groups the cephalis alone represents the whole shell. Therefore in 1882, Bütschli, in the paper mentioned above (p. 1016), maintained the opinion, that these two groups were identical. But there is this important difference between them, that in the Zygospyrida (as in all Spyroidea) the cephalis is bilocular, with a sagittal constriction, separating the right and left chambers. In the Monocyrtida, however (as in all Cyrtoidea), the cephalis is unilocular, forming a quite simple chamber without sagittal constriction. Correspondingly the primary sagittal ring in all Zygospyrida is well preserved and usually complete, while in the Monocyrtida it is never complete, and often quite absent. Another difference is indicated by the form of the central capsule, which in the Zygospyrida is usually bilobed, and more developed in the frontal axis, whilst in the Monocyrtida it is commonly ovate, and more developed in the principal axis.

The important questions of the origin and phylogenetical relation of these two similar groups of Nassellaria form a very complicated and difficult problem, and we do not at present possess the means of solving it. It may be that a part of the Monocyrtida has been derived from the Zygospyrida (as Bütschli erroneously supposes for all), but the contrary is also possible. A third possibility is the independent origin of both groups from the Semantida. But we shall see afterwards, in the description of the Monocyrtida, that a great part of this group may with greater probability be derived from the Plectoidea than from the Stephoidea, and that another part of them has probably been derived quite independently from the Nassellida. Regarding the complicated relations of these similar groups, mentioned above (pp. 892-894), it seems hopeless here to discuss further their difficult affinities; but in any case it seems useful or even necessary to separate the Monocyrtida from the Zygospyrida.

The cephalis of the Zygospyrida possesses all the characteristic features which we have described above as belonging to the Spyroidea in general (p. 1017), and a survey of the Pls. 84-87 exhibits the most important modifications of its shape (compare also Pl. 95, figs. 1-13). Therefore we may avoid useless repetitions by referring to the description given above. We will only point out that the bilocular character of the cephalis (in opposition to the simple cephalis of the Monocyrtida) in the majority of Zygospyrida is apparent on the first view, and that it is always demonstrated by an accurate examination of the sagittal ring and its relation to the longitudinal constriction of the cephalis (compare p. 1019). The basal plate or cortinar plate exhibits usually four typical pores (two smaller jugular, i, and two larger cardinal, k), but this is by no means a general rule, as Bütschli thought; moreover, instead of four cortinar pores, there are frequently found three or six or some other numbers (compare above, p. 1018).

The top of the cephalis in the majority of Zygospyrida bears an apical horn, as an upper prolongation of the dorsal rod of the sagittal ring; it is often of unusual size and shape (Pl. 85, figs. 5-11; Pl. 95, fig. 8, &c.). In several genera two lateral or frontal horns are developed on both sides of the former (Pl. 84, figs. 9-12; Pl. 86, figs. 5-13). Sometimes these two alone are present, while the original apical horn is lost by reduction (Pl. 95, fig. 12). In other genera the apical face bears no horns; probably they are lost by reduction.

The greatest variety of forms is produced in the Zygospyrida by the different number, disposition, and shape of the feet, or the basal apophyses arising from the base of the cephalis. Regarding these remarkable differences, we may distinguish eight subfamilies. The common ancestral group of all are probably the Tripospyrida, which possess the three typical basal feet of Cortina and Cortiniscus, an odd caudal and two paired pectoral feet (Pl. 84). From these may be derived the Dipospyrida (Pl. 85) by loss of the caudal foot, the Tetraspyrida by development of an odd sternal foot (Pl. 53, figs. 7, 8, 19), and the Hexaspyrida by development of three secondary interradial between the three primary perradial feet. The Pentaspyrida may have been derived from the latter by loss of the sternal foot (Pl. 95, figs. 9-11), and the Therospyrida by loss of the two sagittal feet (Pl. 89, figs. 5, 6). The Polyspyrida bear numerous (seven to twelve or more, often twenty to thirty) basal feet, forming a corona around the cortinar plate (Pl. 87); they may have been derived from the Tripospyrida or Hexaspyrida by further multiplication of the feet. Finally, the Circospyrida exhibit no feet at all (Pl. 89, figs. 7-12); they may be derived either from one of the preceding groups by complete reduction and loss of the basal apophyses, or directly from those Semantida which have no feet (Semantis, Semantrum, Clathrocircus, &c.).

Synopsis of the Genera of Zygospyrida.

I. Subfamily Tripospyrida. Three basal feet. (One odd caudal and two paired pectoral.) Apex of the shell with one horn, 441. Tripospyris.

Apex of the shell with three horns, 442. Triceraspyris.

Apex of the shell without horns, 443. Tristylospyris.

Apex with two large coryphal holes, right and left, 444. Cephalospyris.

II. Subfamily Dipospyrida. Two basal lateral feet. (Originally the two pectoral feet.) Two feet free, not grown together. Feet simple, not branched, without lateral spines. One horn, 445. Dipospyris.

No horn, 446. Brachiospyris.

Feet branched like a tree. One horn, 447. Dendrospyris.

Feet with a series of lateral spines. One horn, 448. Dorcadospyris.

Two feet grown together and uniting to form a ring. Apex with a horn. Feet simple, 449. Gamospyris.

Feet with a series of lateral spines, 450. Stephanospyris.

III. Subfamily Tetraspyrida. Two sagittal and two lateral feet. Feet simple, not branched. Apex with one horn, 451. Tetraspyris.

Apex without a horn, 452. Tessarospyris.

IV. Subfamily Hexaspyrida. Six basal feet. Two sagittal, two pectoral, and two tergal feet. Apex with one horn, 453. Hexaspyris.

Apex with three horns, 454. Liriospyris.

Apex without a horn, 455. Cantharospyris.

V. Subfamily Pentaspyrida. Five basal feet. One caudal, two pectoral, and two tergal feet. Apex with one horn, 456. Clathrospyris.

Apex with three horns, 457. Ægospyris.

Apex without a horn, 458. Pentaspyris.

VI. Subfamily Therospyrida. Four paired lateral feet. (Two pectoral and two tergal.) Apex with one horn, 459. Zygospyris.

Apex with three horns (one apical and two frontal), 460. Elaphospyris.

Apex with two lateral or frontal horns, 461. Taurospyris.

Apex without a horn, 462. Therospyris.

VII. Subfamily Polyspyrida. Numerous (seven to twelve or more) basal feet. Apex with one horn, 463. Petalospyris.

Apex with three horns (one apical and two frontal), 464. Anthospyris.

Apex with numerous horns, 465. Ceratospyris.

Apex without a horn, 466. Gorgospyris.

VIII. Subfamily Circospyrida. No basal feet. Apex with one horn, 467. Circospyris.

Apex without a horn, 468. Dictyospyris.

I. Subfamily Tripospyrida. Three basal feet. (One odd caudal and two paired pectoral.)

Apex of the shell with one horn,

441. Tripospyris.

Apex of the shell with three horns,

442. Triceraspyris.

Apex of the shell without horns,

443. Tristylospyris

Apex with two large coryphal holes, right and left,

444. Cephalospyris.

II. Subfamily Dipospyrida. Two basal lateral feet. (Originally the two pectoral feet.)

Two feet free, not grown together.

Feet simple, not branched, without lateral spines.

One horn,

445. Dipospyris.

No horn,

446. Brachiospyris.

Feet branched like a tree.

One horn,

447. Dendrospyris.

Feet with a series of lateral spines.

One horn,

448. Dorcadospyris.

Two feet grown together and uniting to form a ring. Apex with a horn.

Feet simple,

449. Gamospyris.

Feet with a series of lateral spines,

450. Stephanospyris.

III. Subfamily Tetraspyrida. Two sagittal and two lateral feet.

Feet simple, not branched.

Apex with one horn,

451. Tetraspyris.

Apex without a horn,

452. Tessarospyris.

IV. Subfamily Hexaspyrida. Six basal feet.

Two sagittal, two pectoral, and two tergal feet.

Apex with one horn,

453. Hexaspyris.

Apex with three horns,

454. Liriospyris.

Apex without a horn,

455. Cantharospyris.

V. Subfamily Pentaspyrida. Five basal feet.

One caudal, two pectoral, and two tergal feet.

Apex with one horn,

456. Clathrospyris.

Apex with three horns,

457. Ægospyris.

Apex without a horn,

458. Pentaspyris.

VI. Subfamily Therospyrida. Four paired lateral feet. (Two pectoral and two tergal.)

Apex with one horn,

459. Zygospyris.

Apex with three horns (one apical and two frontal),

460. Elaphospyris.

Apex with two lateral or frontal horns,

461. Taurospyris.

Apex without a horn,

462. Therospyris.

VII. Subfamily Polyspyrida. Numerous (seven to twelve or more) basal feet.

Apex with one horn,

463. Petalospyris.

Apex with three horns (one apical and two frontal),

464. Anthospyris.

Apex with numerous horns,

465. Ceratospyris.

Apex without a horn,

466. Gorgospyris.

VIII. Subfamily Circospyrida. No basal feet.

Apex with one horn,

467. Circospyris.

Apex without a horn,

468. Dictyospyris.

Subfamily 1. Tripospyrida, Haeckel, 1881, Prodromus, p. 441.

Definition.—Zygospyrida tripoda, with three descending basal feet (the same as in Cortina, an odd posterior or caudal foot and two paired anterior or pectoral feet).

Genus 441. Tripospyris,^[59] Haeckel, 1881, Prodromus, p. 441.

Definition.—Zygospyrida with three basal feet and one apical horn.

The genus Tripospyris (Pl. 84, figs. 1-7) is in the large group of Spyroidea probably the most original and typical form, from which, as a common ancestral form, all other genera of this polymorphous suborder may be derived. The shell is usually shaped like a nut or thorax, and exhibits two paired lateral chambers, which are separated by a distinct sagittal ring and a slighter or deeper sagittal constriction. The dorsal rod of the ring is prolonged at the upper pole into an ascending apical horn, at the lower pole into a descending caudal foot, whilst two paired pectoral or lateral feet arise from the anterior pole of the basal rod. These three divergent basal feet and the apical horn are the same four typical radial spines which we have encountered already in Plagoniscus (Plagonida), in Plectaniscus (Plectanida), in Cortina (Stephanida), and in Cortiniscus (Semantida). Compare above, p. 891. From all these Plectellaria, Tripospyris differs in the development of a complete bilocular lattice-shell, having the characters of the true Spyroidea. The numerous species of this genus may be placed in different subgenera, according to the different number of collar pores or cortinar pores in the basal plate (two, three, four, six, or more). These differences are very important, however difficult to make out; the following system therefore is a provisional one, and requires further accurate observations.

Subgenus 1. Tripospyrantha, Haeckel.

Definition.—Basal plate with two large pores only (the primary jugular pores of Semantis).

1. Tripospyris cortina, n. sp. (Pl. 95, fig. 1).

Shell ovate, smooth, about as long as broad, with slight ovate sagittal stricture, and broad primary ring in its wall. Basal plate with two large kidney-shaped collar pores only (cardinal pores). Facial and occipital plates each with two pairs of large annular pores, and ten to twelve pairs of small lateral pores. Apical horn and the three basal feet of equal length, one and a half times as long as the shell, three-sided prismatic, straight, divergent.

Dimensions.—Shell 0.08 long, 0.09 broad; horn and feet 0.15 long.

Habitat.—Central Pacific, Station 271, depth 2425 fathoms.

2. Tripospyris cortiniscus, n. sp. (Pl. 84, fig. 6).

Shell ovate, smooth, one and a third times as long as broad, with sharp ovate sagittal stricture and broad primary ring. Basal plate with two large cardinal pores only. Occipital plate with two pairs of very large pores; facial plate and lateral sides with numerous smaller irregular roundish pores. Apical horn small, conical, curved, half as long as the three basal feet, which are club-shaped and three-edged, with thinner bases and half as long as the shell, strongly divergent.

Dimensions.—Shell 0.12 long, 0.09 broad; horn 0.03 long, feet 0.06 long.

Habitat.—Central Pacific, Station 266, depth 2750 fathoms.

3. Tripospyris semantis, n. sp. (Pl. 84, figs. 2, 3).

Shell subspherical, smooth, somewhat broader than long, with slight sagittal stricture and subcircular parietal primary ring. Basal plate with two large semicircular cardinal pores. Facial and occipital plate each with two pairs of large annular pores and an odd large subapical pore; lateral sides with very numerous small roundish pores. Apical horn and caudal foot club-shaped, half as long as the shell, angular, simple; the two pectoral feet somewhat longer, nearly vertical, and at the distal end with a small incision, nearly forked.

Dimensions.—Shell 0.1 long, 0.12 broad; horn and feet 0.05 to 0.07 long.

Habitat.—North Pacific, Station 244, depth 2900 fathoms.

4. Tripospyris diomma, n. sp. (Pl. 84, fig. 5).

Shell thorax-shaped, smooth, twice as broad as long, with deep sagittal stricture, two vaulted ovate bosoms and smaller ovate internal primary ring. Basal plate with two large ovate cardinal pores. Facial plate with three pairs, occipital plate with four pairs of large annular pores; the other lattice-work loose, with small and numerous irregular polygonal pores. Apical horn and caudal feet slender and thin, curved, shorter than half the shell; two pectoral feet also small, widely divergent, more or less curved, deeply forked.

Dimensions.—Shell 0.1 long, 0.16 broad; horn and feet 0.2 to 0.25 long.

Habitat.—South Atlantic, Station 332, depth 2200 fathoms.

Subgenus 2. Tripospyrella, Haeckel.

Definition.—Basal plate with three large collar pores (two paired posterior cardinal pores, and an odd anterior sternal pore).

5. Tripospyris triomma, Haeckel.

Ceratospyris triomma, Ehrenberg, 1875, Abhandl. d. k. Akad. d. Wiss. Berlin, p. 66, Taf. xxi. fig. 3.

Shell subspherical, tuberculate, with slight sagittal stricture and circular internal ring. Basal plate with three large pores, which are sometimes (but not in every specimen) surrounded by a circle of very small pores. The other lattice-work with numerous small roundish pores. Apical horn small, oblique, about as long as the shell. Three feet very large, cylindrical, curved, widely divergent, four to five times as long as the shell. (In Ehrenberg's description the caudal foot is erroneously described as "frontal spine"; its figure exhibits the basal plate.)

Dimensions.—Shell 0.07 to 0.09 diameter; horn 0.06 long, feet 0.3 to 0.4 long.

Habitat.—Fossil in Tertiary rocks of Barbados.

6. Tripospyris conifera, n. sp. (Pl. 84, figs. 7, 7a).

Shell nearly hemispherical, papillate, with slight sagittal stricture and semicircular internal ring. Basal plate with three large pores (sometimes, as in the figured specimen, with some small accessory peripheral pores). The other lattice-work with subregular circular pores. Apical horn shorter than the three basal feet, but of similar form, like an elegant ovate dimpled cone, spinulate, with a smooth spindle-shaped pedicle, about as long as the shell.

Dimensions.—Shell 0.08 long, 0.1 broad; horn 0.06 long, feet 0.08 long.

Habitat.—Western Tropical Pacific, Station 225, depth 4475 fathoms.

7. Tripospyris triplecta, n. sp. (Pl. 95, fig. 2).

Shell thorax-shaped, spiny, with deep sagittal stricture and semicircular internal ring. Basal plate with three large collar pores. Facial plate with four pairs, occipital plate with three pairs of large annular pores; the other pores small, subregular, circular. Apical horn and the feet slender, three-sided pyramidal, about as long as the shell.

Dimensions.—Shell 0.1 long, 0.11 broad; horn and feet 0.1 to 0.15 broad.

Habitat.—Mediterranean, Corfu (Haeckel), surface.

Subgenus 3. Tripospyrissa, Haeckel.

Definition.—Basal plate with two pairs of collar pores (two larger posterior cardinal pores and two smaller anterior jugular pores).

8. Tripospyris semantrum, n. sp. (Pl. 95, fig. 3).

Shell thorax-shaped, thorny, with deep sagittal stricture and subcircular ring. Basal plate with four large collar pores (two smaller ovate jugular, and two larger pentagonal cardinal pores). Facial and occipital plates also each with two pairs of large annular pores; lateral sides with smaller irregular polygonal pores. Apical horn and the three feet slender, prismatic, divergent, longer than the shell.

Dimensions.—Shell 0.07 long, 0.08 broad; horn and feet 0.11 to 0.13 long.

Habitat.—South Atlantic, Cape of Good Hope (Wilhelm Bleek), surface.

9. Tripospyris capitata, n. sp. (Pl. 84, fig. 1).

Shell subspherical, spiny, with slight sagittal stricture and ovate internal ring. Basal plate with four large collar pores. Facial plate with three pairs and occipital plate with two pairs of large roundish annular pores; lateral lattice with smaller irregular pores. Apical horn and the three feet subcylindrical, about half as long as the shell, straight, divergent, with a spherical, spinulate knob at the distal end.

Dimensions.—Shell 0.09 long, 0.1 broad; horn and feet 0.05 to 0.06 long.

Habitat.—Central Pacific, Station 266, depth 2750 fathoms.

10. Tripospyris clavata, Haeckel.

Ceratospyris clavata, Bütschli, 1882, Zeitschr. f. wiss. Zool., vol. xxxvi. p. 539, Taf. xxxii. fig. 13, a-c.

Shell subspherical, compressed, rough, with slight sagittal stricture and ovate internal primary ring. Basal plate with four large collar pores (fig. 13a, loc. cit.). The other lattice-work with irregular small roundish pores. Apical horn and the three feet short and thick, scarcely half as long as the shell, with a roundish spinulate knob at the distal end.

Dimensions.—Length of the shell 0.07 long, 0.08 broad; horn and feet 0.02 to 0.03 long.

Habitat.—Fossil in Barbados.

11. Tripospyris tessaromma, n. sp.

Shell nearly cubical, spiny, with deep sagittal stricture and subcircular ring. Basal plate with four large collar pores. Facial and occipital plates each also with two pairs of large square annular pores; lateral pores irregular polygonal. Apical horn half as long as the feet, which are three times the length of the shell, cylindrical, slightly curved.

Dimensions.—Shell 0.1 long, 0.12 broad; horn 0.15 long, feet 0.3 long.

Habitat.—Tropical Atlantic, Station 348, depth 2450 fathoms.

Subgenus 4. Tripospyromma, Haeckel.

Definition.—Basal plate with six or more collar pores. Commonly two small anterior jugular pores, two large middle cardinal pores, and two small posterior cervical pores; sometimes several small accessory collar pores.

12. Tripospyris hexomma, n. sp. (Pl. 95, fig. 4).

Shell thorax-shaped, tuberculate, with deep sagittal stricture and semicircular internal primary ring. Basal plate with three pairs of pores. Facial plate with two pairs, occipital plate with four pairs of large annular pores. Lateral pores smaller, irregular, polygonal. Apical horn and caudal foot half as long as the shell and as the two pectoral feet; all four spines cylindrical, two to three times as long as the shell, slightly curved.

Dimensions.—Shell 0.1 long, 0.12 broad; horn and feet 0.2 to 0.4 long.

Habitat.—Central Pacific, Station 265, depth 2900 fathoms.

13. Tripospyris semantidium, n. sp.

Shell nut-shaped, thorny, with sharp sagittal stricture and subcircular ring. Basal plate with three pairs of large pores. Facial and occipital plates each with three pairs of large squarish pores. Lateral pores small and numerous, irregular roundish. Apical horn half as long as the shell and the three feet; all four spines straight, cylindrical, with thickened club-shaped end.

Dimensions.—Shell 0.12 long, 0.13 broad; horn 0.06 long, feet 0.15.

Habitat.—Tropical Atlantic, Station 347, depth 2250 fathoms.

14. Tripospyris eucolpos, n. sp. (Pl. 84, fig. 4).

Shell thorax-shaped, smooth, with two vaulted bosoms, separated by a deep sagittal stricture and an internal primary ring. Basal plate constricted, with three pairs of collar pores. The other lattice-work with subregular circular pores. Apical horn and the three feet shorter than the shell, straight, divergent; their inner half thinner, cylindrical, smooth, their outer half an ovate dimpled cone.

Dimensions.—Shell 0.1 long, 0.13 broad; horn and feet 0.06 long.

Habitat.—Indian Ocean, Cocos Islands (Rabbe), surface.

15. Tripospyris tribrachiata, Haeckel.

Cladospyris tribrachiata, Ehrenberg, Abhandl. d. k. Akad. d. Wiss. Berlin, p. 68, Taf. xxi. fig. 8.

Shell subspherical, smooth, with slight sagittal stricture and numerous, very small circular pores. Basal plate with numerous small pores. Apical horn and the three divergent feet very large and stout, straight, three-sided prismatic, with dentate edges, two to three times as long as the shell.

Dimensions.—Shell diameter 0.05; horn and feet 0.1 to 0.15 long.

Habitat.—Fossil in Barbados.

16. Tripospyris furcata, n. sp. (Pl. 83, fig. 11).

Shell nut-shaped, smooth, with deep sagittal stricture and broad ring. Basal plate with three pairs of small pores. Facial and occipital plates each with a pair of very large holes. Apical horn and caudal foot simple conical, two pectoral feet forked or irregularly branched.

Dimensions.—Shell 0.08 long, 0.12 broad; horn and feet 0.05 long.

Habitat.—Central Pacific, Station 271, depth 2425 fathoms.

Genus 442. Triceraspyris,^[60] Haeckel, 1881, Prodromus, p. 441.

Definition.—Zygospyrida with three basal feet and three coryphal horns.

The genus Triceraspyris has arisen from the preceding ancestral Tripospyris by the development of two paired frontal horns, so that the shell here bears six appendages, three superior or coryphal spines and three inferior or basal spines; two of these are odd and dorsal (the apical horn and the caudal foot), the four others are paired and ventral (the frontal horns and the pectoral feet). The numerous species of this genus may be divided into three subgenera, according to the simple or branched shape of the ascending horns and of the descending feet.

Subgenus 1. Triospyris, Haeckel, 1881, Prodromus, p. 441.

Definition.—Horns and feet simple, not branched nor forked.

1. Triceraspyris tripodiscus, n. sp.

Shell nut-shaped, tuberculate, with deep sagittal stricture. Pores irregular roundish, two pairs of larger pores on each side of the ring. Basal plate with three large pores. Horns and feet slender cylindrical, straight, divergent; three horns about as long as the shell, three feet twice as long.

Dimensions.—Shell 0.06 long, 0.08 broad; horn 0.05 long, feet 0.1.

Habitat.—Central Pacific, Stations 270 to 274, depth 2350 to 2925 fathoms.

2. Triceraspyris cortiniscus, n. sp.

Shell subspherical, smooth, with slight sagittal stricture. Pores small and numerous, subregular roundish. Basal plate with two large pores (?). Apical horn conical, short, half as long as the shell and the two lateral horns, which are curved outwards. All three feet equal, cylindrical, strongly curved and divergent, twice to three times as long as the shell.

Dimensions.—Shell 0.07 long, 0.08 broad; horn 0.04 to 0.08 long, feet 0.15 to 0.2 long.

Habitat.—Central Pacific, Station 265, depth 2900 fathoms.

3. Triceraspyris didiceros, Haeckel.

Ceratospyris didiceros, Ehrenberg, 1875, Abhandl. d. Akad. d. Wiss. Berlin, p. 66, Taf. xxi. fig. 6.

Shell nut-shaped, thorny, with superficial sagittal stricture. Pores large, irregular roundish. Basal plate with four larger pores. Apical horn and caudal foot small, conical, shorter than half the shell. The two frontal horns longer, slender conical. The two pectoral feet very large, cylindrical, nearly parallel, vertical, slightly curved, twice to three times as long as the shell.

Dimensions.—Shell 0.07 long, 0.09 broad; two sagittal spines 0.02 long, two lateral horns 0.04 long, two lateral feet 0.15 to 0.25 long.

Habitat.—Fossil in Barbados.

Subgenus 2. Triospyrium, Haeckel.

Definition.—Horns simple, not branched; feet forked or branched.

4. Triceraspyris furcata, Haeckel.

Ceratospyris furcata, Ehrenberg, 1875, Abhandl. d. k. Akad. d. Wiss. Berlin, p. 66, Taf. xx. fig. 8.

Shell nut-shaped, tuberculate, with slight sagittal stricture. Pores numerous, irregular roundish. Basal plate with four large pores. Three horns small, conical, shorter than half the shell. Three feet large, cylindrical, curved, about twice as long as the shell, forked at the distal end.

Dimensions.—Shell 0.07 long, 0.08 broad; horns 0.02 long, feet 0.1 to 0.12 long.

Habitat.—Fossil in Barbados.

5. Triceraspyris giraffa, n. sp. (Pl. 84, fig. 11).

Shell nut-shaped, mammillate, with slight sagittal stricture. Pores numerous, subregular circular. Basal plate with nine pores (three larger central and three alternate pairs of smaller peripheral, as in Pl. 87, fig. 2). Three horns equal, straight, divergent, shorter than the shell, in the basal half cylindrical, in the distal half spindle-shaped. Three feet cylindrical, twice as long as the shell, nearly parallel, vertical, at the distal end divergent, with a recurved branch near the base.

Dimensions.—Shell 0.08 long, 0.1 broad; horns 0.05 to 0.07 long, feet 0.16 long.

Habitat.—Western Tropical Pacific, Station 225, depth 4475 fathoms.

6. Triceraspyris gazella, n. sp. (Pl. 84, fig. 9).

Shell nut-shaped, tuberculate, with sharp sagittal stricture. Pores large, irregular roundish; two or three pairs of larger pores on each side of the ring. Basal plate with three large triangular pores. Three horns simple, about as long as the shell, the apical straight, the two frontal elegantly curved. Three feet somewhat longer, slender, curved, with a recurved branch near the base, repeatedly forked at the distal end.

Dimensions.—Shell 0.06 long, 0.09 broad; horn 0.05 long, feet 0.08 long.

Habitat.—Indian Ocean (Cocos Islands), surface (Rabbe).

7. Triceraspyris corallorrhiza, n. sp. (Pl. 84, fig. 12).

Shell nut-shaped, spiny, with deep sagittal stricture. Pores irregular polygonal or roundish. Basal plate with two large semicircular pores. Three horns slender, simple, about half as long as the shell. Three feet of the same length, slender, divergent, irregularly branched like coral.

Dimensions.—Shell 0.06 long, 0.09 broad; horn and feet 0.03 to 0.05 long.

Habitat.—South Atlantic, Station 332, depth 2200 fathoms.

8. Triceraspyris maniculata, n. sp.

Shell subspherical, smooth, without external sagittal stricture. Pores subregular circular. Basal plate with four large pores (?). Three horns simple, straight, divergent, spindle-shaped, half as long as the shell. Caudal foot of the same form, twice as long. Two pectoral feet cylindrical, curved, twice as long as the shell, palmate, divided at the distal end into five short fingers.

Dimensions.—Shell 0.08 diameter; horns 0.04 long; lateral feet 0.12 long.

Habitat.—North Pacific, Station 241, depth 2300 fathoms.

9. Triceraspyris longicornis, n. sp.

Shell nut-shaped, papillate, with deep sagittal stricture. Pores irregular roundish. Basal plate with six pores (?). Apical horn short, conical, two frontal horns very large, curved, widely divergent, longer than the shell. Three feet of about the same length, irregularly branched.

Dimensions.—Shell 0.08 long, 0.12 broad; lateral horns and feet 0.15 to 0.2 long.

Habitat.—Tropical Atlantic, Station 348, depth 2450 fathoms.

Subgenus 3. Triospyridium, Haeckel.

Definition.—Horns and feet forked or branched.

10. Triceraspyris damaecornis, n. sp.

Shell nut-shaped, smooth, compressed, with broad sagittal ring. Pores irregular roundish; one pair of very large pores on each side of the ring. Basal plate with four large collar pores. Three horns and three feet short, divergent, slightly curved, about half as long as the shell, irregularly branched. (In general form very similar to Elaphospyris damaecornis, Pl. 84, fig. 10, with which I formerly confounded it.)

Dimensions.—Shell 0.08 long, 0.12 broad; horns and feet 0.04 long.

Habitat.—South Pacific, Station 295, depth 1500 fathoms.

11. Triceraspyris arborescens, n. sp.

Shell subspherical, with deep sagittal stricture. Pores irregular roundish; three pairs of larger pores on both sides of the ring. Basal plate with two large collar pores. Three horns about half as long as the shell, with few irregular terminal branches. (Beginning of a cupola.) Three feet strong, cylindrical, twice as long as the shell, richly branched, arborescent.

Dimensions.—Shell 0.09 long, 0.1 broad; horns 0.05 long, feet 0.2 long.

Habitat.—Indian Ocean (Madagascar), Rabbe, surface.

Genus 443. Tristylospyris,^[61] Haeckel, 1881, Prodromus, p. 441.

Definition.—Zygospyrida with three basal feet, without apical horn.

The genus Tristylospyris exhibits in general the same structure as the typical genus Tripospyris, its ancestral form. It differs from the latter in the absence of the apical horn, which is completely reduced, and may therefore be regarded as the simplest prototype of all tripodal Cyrtellaria without a horn.

Subgenus 1. Tristylospyrula, Haeckel.

Definition.—Feet simple, not branched nor forked.

1. Tristylospyris palmipes, n. sp. (Pl. 84, fig. 14).

Shell companulate, smooth, with slight sagittal stricture. Pores irregular roundish, three pairs of larger annular pores on each side of the broad ring. Basal plate with four large collar pores. Feet half as long as the shell, slightly divergent, straight, prismatic, with a broad, hand-like, radially striped plate at the distal end.

Dimensions.—Shell 0.1 long, 0.09 broad; feet 0.06 long.

Habitat.—Equatorial Atlantic, Station 347, depth 2250 fathoms.

2. Tristylospyris scaphipes, n. sp. (Pl. 84, fig. 13).

Shell nut-shaped, smooth, with sharp sagittal stricture. Pores very small and numerous, circular; two pairs of larger pores on both sides of the ring. Basal plate with four large pores (?). Feet about half as long as the shell, angular, shovel-shaped, straight, parallel, vertical.

Dimensions.—Shell 0.06 long, 0.08 broad; feet 0.04 long.

Habitat.—North Pacific, Station 244, depth 2900 fathoms.

3. Tristylospyris clavipes, n. sp. (Pl. 84, fig. 15).

Shell nut-shaped, rough, with deep sagittal stricture. Pores small, subregular circular. Basal plate with three large pores. Feet about as long as the shell, slender, straight, divergent, with a spinulate knob at the thickened distal end.

Dimensions.—Shell 0.06 long, 0.08 broad; feet 0.05 long.

Habitat.—Central Pacific, Station 272, depth 2600 fathoms.

4. Tristylospyris triceros, Haeckel.

Ceratospyris triceros, Ehrenberg, 1875, Abhandl. d. k. Akad. d. Wiss. Berlin, p. 66, Taf. xxi. fig. 5.

Shell nut-shaped, tuberculate, without external sagittal stricture. Pores circular, not numerous. Basal plate with four large collar pores. Feet large, cylindrical, three to four times as long as the shell, strongly curved and divergent.

Dimensions.—Shell 0.05 long, 0.07 broad; feet 0.15 to 0.2 long.

Habitat.—Fossil in Barbados.

Subgenus 2. Tristylospyrium, Haeckel.

Definition.—Feet forked or branched.

5. Tristylospyris furcata, n. sp.

Shell subspherical, rough, with slight sagittal stricture. Pores subregular circular. Basal plate with three large collar pores. Feet cylindrical, three to four times as long as the shell, strongly curved and divergent, at the distal end forked, with two short (sometimes ramified) branches.

Dimensions.—Cephalis 0.08 long, 0.09 broad; feet 0.2 to 0.3 long.

Habitat.—South Atlantic (off Patagonia), Station 318, surface.

6. Tristylospyris ramosa, n. sp. (Pl. 52, fig. 23).

Shell subspherical, tuberculate, with a prominent sagittal ring. Pores irregular roundish. Basal plate with three large pores. Feet large, straight, widely divergent, about twice as long as the shell, prismatic, irregularly branched. (Compare the following species.)

Dimensions.—Shell 0.08 in diameter; feet 0.15 long.

Habitat.—Central Pacific, Station 265, depth 2900 fathoms.

7. Tristylospyris tripodiscium, n. sp. (Pl. 52, fig. 22).

Shell subovate, tuberculate, very similar to the preceding species. It differs from this in the very different size of the irregular pores and the greater breadth of the pedal branches. The basal plate in a complete specimen (observed afterwards from the base) exhibited four large collar pores of the usual form, whilst in the similar preceding species it had three pores. In the similar Tripodiscium sphærocephalum (Pl. 52, fig. 21) the basal mouth is quite simple and open.

Dimensions.—Shell 0.09 long, 0.1 broad; feet 0.12 long.

Habitat.—Central Pacific, Station 268, depth 2900 fathoms.

Genus 444. Cephalospyris,^[62] Haeckel, 1881, Prodromus, p. 441 (sensu emend.).

Definition.—Zygospyrida with three basal feet and two large apical openings or coryphal holes, one on each side of the ring-apex. No true horns.

The genus Cephalospyris comprises some few Tripospyrida of very peculiar shape, differing from all other Zygospyrida in the possession of two large apical holes or coryphal apertures, lying on each side of a latticed sagittal septum, which is formed by the upper part of the sagittal ring. The sagittal stricture is deep, with a complete primary ring. The vertical axis of the slender ovate shell is much greater than the transverse. The network is very delicate, with very small and numerous triangular or polygonal pores. The central capsule encloses peculiar concrements (Pl. 96, fig. 28).

1. Cephalospyris cancellata, n. sp. (Pl. 83, fig. 10).

Shell slender ovate, two and a half times as long as broad, with deep sagittal stricture and complete ring. Network very delicate, with very small and numerous, irregular polygonal pores. The two large apical holes are separated by a latticed triangular sagittal septum, the apex of which represents a rudimentary horn. Basal plate with two large collar holes. Three feet slightly curved, divergent, about half as long as the breadth of the shell; the caudal foot slender, much thinner than the two stout pyramidal pectoral feet.

Dimensions.—Shell 0.32 long, 0.13 broad.

Habitat.—Central Pacific, Station 272, depth 2600 fathoms.

2. Cephalospyris ovata, n. sp.

Shell slender, ovate, twice as long as broad, with deep sagittal stricture and complete ring. Network very delicate, with very small and numerous triangular pores (on both poles intermingled with irregular polygonal pores). The two large apical holes are separated by a latticed triangular sagittal septum, the upper edge of which is concave and bears two rudimentary horns. Basal plate with four large collar holes. Three feet latticed, slightly curved, convergent, scarcely one-eighth as long as the breadth of the shell. The central capsule filled up by concrements.

Dimensions.—Shell 0.32 long, 0.16 broad.

Habitat.—Central Pacific, Station 271, depth 2425 fathoms.

3. Cephalospyris triangulata, n. sp. (Pl. 96, fig. 28).

Shell ovate, one and a half times as long as broad, with deep sagittal stricture and complete ring. Network very delicate and regular, with small triangular pores of equal size. The two large apical holes are separated by a latticed semilunar septum, the upper edge of which is concave, and bears two rudimentary horns. Basal plate with three large collar holes (?). Three feet latticed, conical, nearly parallel and vertical (the caudal curved), about half as long as the breadth of the shell. The ovate central capsule contains peculiar amyloidal concentric concrements.

Dimensions.—Shell 0.2 long, 0.14 broad.

Habitat.—Central Pacific, Station 274, depth 2750 fathoms.

Subfamily 2. Dipospyrida, Haeckel, 1881, Prodromus, p. 441.

Definition.—Zygospyrida dipoda, with two descending lateral basal feet (probably corresponding to the pectoral feet of Cortina).

Genus 445. Dipospyris,^[63] Haeckel, 1881, Prodromus, p. 441.

Definition.—Zygospyrida with two simple free basal feet and one apical horn.

The genus Dipospyris and the following five genera represent together the interesting subfamily of Dipospyrida, which always bear two opposite lateral feet only. Therefore in this bipedal group the biradial or bilateral type of the Spyroidea is particularly expressed. Such bipedal forms never occur in the Cyrtoidea. The topographical relation of the two lateral feet to the rods of the collar-plate, and to the cortinar pores separated by these, leaves no doubt that they correspond to the pectoral feet of Cortina and Tripospyris, and therefore that the Dipospyrida have originated from the Tripospyrida by loss of the caudal foot. Dipospyris is the simplest form of the Dipospyrida, with two simple free feet.

1. Dipospyris bipes, n. sp.

Shell thorax-shaped, smooth, with deep sagittal stricture, two vaulted bosoms, and subregular circular pores. Basal plate with two large collar pores only. Horn and feet equal, conical, straight, about as long as the shell; the feet widely divergent.

Dimensions.—Shell 0.08 long, 0.12 broad; horn and feet 0.1 to 0.15 long.

Habitat.—Fossil in Barbados.

2. Dipospyris mystax, Haeckel.

Ceratospyris mystax, Ehrenberg, 1875, Abhandl. d. k. Akad. d. Wiss. Berlin, p. 66, Taf. xx. fig. 6.

Shell elliptical spinulate, with slight collar stricture and large subregular circular pores. Basal plate with three pores (?) Horn small conical, oblique, shorter than the shell. Feet slender conical, longer than the shell, slightly curved, divergent. At the base of the columella, between the two feet, a small rudiment of the last caudal foot is visible.

Dimensions.—Shell 0.06 long, 0.1 broad; horn 0.02, feet 0.12 long.

Habitat.—Fossil in Barbados.

3. Dipospyris cubus, n. sp. (Pl. 83, fig. 18).

Shell box-shaped, subcubical, papillate, without external sagittal stricture, with numerous subregular circular pores. Basal plate with three very large collar pores, surrounded by a circle of smaller pores. Apical horn short and thick, scarcely half as long as the shell. Feet of the same form, longer than the shell, widely divergent.

Dimensions.—Shell 0.08 long, 0.11 broad; horn 0.03 long, feet 0.14 long.

Habitat.—Central Pacific, Station 272, depth 2600 fathoms.

4. Dipospyris chelifer, n. sp. (Pl. 85, fig. 3).

Shell elliptical, compressed, nodose, with deep sagittal stricture and irregular roundish pores. Basal plate with three pores (?). Apical horn stout, conical, twice to four times as long as the shell (often much longer than in the figured specimen). Feet scarcely longer then the shell, cylindrical, slightly curved towards one another.

Dimensions.—Shell 0.08 long, 0.12 broad; horn 0.2 to 0.3 long, feet 0.1 to 0.15 long.

Habitat.—Central Pacific, Station 268, depth 2900 fathoms.

5. Dipospyris irregularis, n. sp. Pl. 85, fig. 2.

Shell subspherical, without external sagittal stricture, with small circular pores. Basal plate with four pores. Apical horn small, conical, shorter than the shell. Feet three to four times as long as the shell, cylindrical, irregularly curved, very variable in size and form.

Dimensions.—Shell 0.08 long, 0.1 broad; horn 0.02 to 0.04 long, feet 0.2 to 0.3 long.

Habitat.—Central Pacific, Stations 266 to 268, depth 2700 to 2900 fathoms.

6. Dipospyris sigmopodium, n. sp.

Shell violin-shaped, thorny, with deep sagittal stricture and irregular roundish pores. Basal plate with four collar pores. Horn straight, conical, about as long as the shell. Feet twice as long, cylindrical, markedly divergent, S-shaped, curved.

Dimensions.—Shell 0.08 long, 0.12 broad; horn 0.06 long, feet 0.2 long.

Habitat.—Tropical Atlantic, Station 348, depth 2450 fathoms; also fossil in Barbados.

7. Dipospyris forcipata, n. sp. (Pl. 85, fig. 1).

Shell nut-shaped, tuberculate, with subregular circular pores. Basal plate with four larger and a circle of six to ten smaller pores. Horn cylindrical, straight, two to three times as long as the shell. Feet three to five times as long as the shell, cylindrical, semicircular, with convergent and crossed distal ends. (If these ends grow together, Gamospyris arises.)

Dimensions.—Shell 0.08 long, 0.11 broad; horn 0.15 to 0.2 long, feet 0.2 to 0.4 long.

Habitat.—Central Pacific, Stations 263 to 268, depth 2600 to 3000 fathoms.

Genus 446. Brachiospyris,^[64] Haeckel, 1881, Prodromus, p. 441.

Definition.—Zygospyrida with two simple free basal feet, without apical horn.

The genus Brachiospyris differs from the preceding Dipospyris, its ancestral form, only in the absence of the reduced apical horn, and therefore bears to it a similar relation to that which the hornless Tristylospyris, among the Tripospyrida, bears to the horned Tripospyris. Brachiospyris may therefore also be derived from Tristylospyris by loss of the caudal foot.

1. Brachiospyris ocellata, Haeckel.

Ceratospyris ocellata, Ehrenberg, 1875, Abhandl. d. k. Akad. d. Wiss. Berlin, p. 66, Taf. xx. fig. 5.

Shell nut-shaped, thorny, with slight sagittal stricture and irregular roundish pores. Basal plate with four large and four alternate pairs of smaller pores. Two feet cylindrical, straight, divergent, two to three times as long as the shell.

Dimensions.—Shell 0.08 long, 0.11 broad; feet 0.2 to 0.3 long.

Habitat.—South Atlantic, Station 335, depth 1425 fathoms; also fossil in Barbados.

2. Brachiospyris diacantha, n. sp. (Pl. 95, fig. 5).

? Ceratospyris diacantha, Ehrenberg, 1872, Monatsber. d. k. preuss. Akad. d. Wiss. Berlin, p. 303.

Shell nut-shaped, tuberculate, compressed in the sagittal axis, convex on the frontal face, concave on the sagittal face, with a slight sagittal stricture; with large irregular roundish pores. Basal plate with three very large pores. Two feet cylindrical, curved, S-shaped, about twice as long as the shell.

Dimensions.—Shell 0.06 long, 0.09 broad; feet 0.1 to 0.15 long.

Habitat.—Western Tropical Pacific (Philippine Sea), Station 206, depth 2100 fathoms.

Genus 447. Dendrospyris,^[65] Haeckel, 1881, Prodromus, p. 441.

Definition.—Zygospyrida with two free lateral feet, forked or branched like a tree. Apex with a horn.

The genus Dendrospyris differs from its ancestral form Dipospyris in the ramification of the two large lateral feet, which descend from the base of the shell, and are usually very large and stout, sometimes simply forked.

1. Dendrospyris stylophora, Haeckel.

Ceratospyris stylophora, Ehrenberg, 1875, Abhandl. d. k. Akad. d. Wiss. Berlin, p. 66, Taf. xx. fig. 10.

Shell nut-shaped, thorny, with subregular circular pores. Basal plate with four pores. Apical horn and the two divergent feet straight, cylindrical, larger than the shell, forked at the distal end. (The size and number of the fork-branches is variable; the horn is sometimes simple. In some specimens a rudimentary remnant of the lost caudal foot is visible.)

Dimensions.—Shell 0.08 long, 0.09 broad; horn and feet 0.1 to 0.12 long.

Habitat.—Fossil in Barbados.

2. Dendrospyris dirrhiza, Haeckel.

Ceratospyris dirrhiza, Ehrenberg, 1875, Abhandl. d. k. Akad. d. Wiss. Berlin, p. 66, Taf. xx. fig. 9.

Shell nut-shaped, spiny, very similar to the preceding species. It differs from that mainly in the growth of the cylindrical feet, which are not straight and divergent, but more or less curved and convergent; their distal ends are sometimes simply forked, sometimes repeatedly dichotomous. The size and form of the apical horn are also very variable.

Dimensions.—Shell 0.06 long, 0.08 broad; horn and feet 0.07 to 0.09 long.

Habitat.—Fossil in Barbados.

3. Dendrospyris bibrachiata, Haeckel.

Cladospyris bibrachiata, Ehrenberg, 1875, Abhandl. d. k. Akad. d. Wiss. Berlin, p. 68, Taf. xxi. fig. 7.

Shell nut-shaped, smooth, with sharp stricture and numerous very small circular pores. Apical horn and the two feet very large and stout, straight, prismatic, with irregular lateral branches on their edges, twice to four times as long as the shell (The horn in the Ehrenberg's figure is broken off.) This species is closely allied to Tripospyris tribrachiata.

Dimensions.—Shell 0.05 long, 0.06 broad; horn and feet 0.1 to 0.2 long.

Habitat.—Fossil in Barbados.

4. Dendrospyris furcata, n. sp.

Shell subspherical, tuberculate, with irregularly roundish pores. Basal plate with two large pores. Apical horn simple, conical, as long as the shell. Feet cylindrical, twice as long, in the proximal half parallel, vertical, in the distal half with two stout divergent equal fork-branches, one of which is directed dorsally, the other ventrally.

Dimensions.—Shell 0.07 long, 0.08 broad; horn 0.06 long, feet 0.1 to 0.15 long.

Habitat.—Tropical Atlantic, Station 338, depth 1990 fathoms.

5. Dendrospyris polyrrhiza, n. sp. (Pl. 85, fig. 8).

Shell subspherical, rough, with subregular circular pores. Basal plate with three pores (?). Apical horn simple, conical, half as long as the shell. Feet cylindrical twice to three times as long as the shell, semicircular, with a strong conical tooth in the middle of their outer convex edge; their distal ends convergent, divided into a bunch of numerous short irregular branches.

Dimensions.—Shell 0.7 long, 0.08 broad; horn 0.03 long, feet 0.15 to 0.25 long.

Habitat.—South Atlantic, Station 332, depth 2200 fathoms.

6. Dendrospyris ramosa, n. sp.

Shell nut-shaped, spiny, with irregular roundish pores. Basal plate with three pairs of pores. Apical horn cylindrical, spinulate, twice to three times as long as the shell. Feet as long as the horn, S-shaped, widely divergent, irregularly branched, with widely distant pointed branches.

Dimensions.—Shell 0.08 long, 0.12 broad; horn and feet 0.2 to 0.3 long.

Habitat.—North Atlantic, Station 353, depth 2965 fathoms.

7. Dendrospyris arborescens, n. sp. (Pl. 85, fig. 9).

Shell nut-shaped, tuberculate, with subregular circular pores. Basal plate with four central larger and ten to twelve peripheral smaller pores. Apical horn cylindrical, twice as long as the shell, in the distal half spinulate or tuberculate. Feet about three times as long as the shell, cylindrical, nearly vertical, in the distal half irregularly branched, with dense bunches of aggregated blunt branches.

Dimensions.—Shell 0.07 long, 0.09 broad; horn and feet 0.12 to 0.18 long.

Habitat.—Equatorial Atlantic, Station 347, depth 2250 fathoms.

Genus 448. Dorcadospyris,^[66] Haeckel, 1881, Prodromus, p. 441.

Definition.—Zygospyrida with two free lateral feet armed with a series of secondary spines. Apex with a horn.

The genus Dorcadospyris and the closely allied Stephanospyris differ from the other Dipospyrida in the development of a series of secondary spines on the convex outer margin of the two large curved lateral feet, which therefore appear semipinnate. In some species this peculiar armature attains an extraordinary size, whilst the shell itself is very small, as in Dorcadospyris dinoceras (Pl. 85, fig. 4).

1. Dorcadospyris dentata, n. sp. (Pl. 85, fig. 6).

Shell subspherical, tuberculate with small regular circular pores. Basal plate with four larger pores. Apical horn three to four times as long as the shell, slender conical, smooth. Feet more or less convexly curved towards one another; the distal ends not crossed. In the convex edge of each arm a series of five to ten smooth conical teeth, not longer than the shell. This common species is very variable and often asymmetrical; the figured specimen is an asymmetrical one, in which the two arms exhibit different curves; in the normal form both arms have the same curve, now more, now less convex.

Dimensions.—Shell 0.06 long, 0.08 broad; horn 0.2, feet 0.03 long.

Habitat.—Central Pacific, Stations 267 to 274, depth 2350 to 2925 fathoms.

2. Dorcadospyris antilope, n. sp. (Pl. 85, fig. 5).

Shell subspherical, tuberculate, with small regular circular pores. Basal plate with four larger pores. Apical horn four to six times as long as the shell, straight, cylindrical, smooth. Feet of the same length, crescentic or nearly semicircular, with crossed distal ends. On the convex edge of each foot a series of twelve to fifteen smooth conical teeth, partly longer than the shell. (Very variable in size and curvature of the feet, and number of their teeth.)

Dimensions.—Shell 0.09 long, 0.11 broad; horn and feet 0.4 to 0.6 long.

Habitat.—Central Pacific, Stations 270 to 274, depth 2350 to 2925 fathoms.

3. Dorcadospyris lunulata, n. sp.

Shell subspherical spinulate, nearly of the same shape as in the preceding species, but with a short conical horn (scarcely as long as the shell); the feet are much mere slender, crescentic, and bear twenty to thirty smaller smooth conical teeth (shorter than the shell). The distal ends of the feet are crossed.

Dimensions.—Shell 0.08 long, 0.09 broad; horn 0.06 long, feet 0.03 to 0.06 long.

Habitat.—Central Pacific, Station 266, depth 2750 fathoms.

4. Dorcadospyris decussata, n. sp. (Pl. 85, fig. 7).

Shell subspherical, smooth, very similar to that of the two preceding species. Horn small conical, about as long as the shell. Feet more than semicircular, more strongly curved than in any other species, each with four to eight small conical teeth, shorter than the shell; distal ends crossed. (In this species also, besides the normal symmetrical form, there often occurs an asymmetrical form of the two feet; one of these frequent anomalies is shown in fig. 7.)

Dimensions.—Shell 0.06 long, 0.08 broad; horn 0.05, feet 0.2 to 0.5 long.

Habitat.—Central Pacific, Stations 265 to 268, depth 2700 to 2900 fathoms.

5. Dorcadospyris dinoceras, n. sp. (Pl. 85, fig. 4).

Shell subspherical, tuberculate, with subregular circular pores. Basal plate with four larger central and eight to twelve smaller peripheral pores. Horn about as long as the shell, in the basal half prismatic, smooth, in the distal half ovate or strobiliform, spiny. Feet very large and strongly curved, together nearly heart-shaped, four to six times as long as the shell. Each foot bears on its outer convex side a series of fifteen to twenty or more strong conical teeth, which are again spinulate, perpendicular to the foot, and longer than the shell.

Dimensions.—Shell 0.08 long, 0.09 broad; horn 0.07 long, feet 0.3 to 0.5 long.

Habitat.—Central Pacific, Station 268, depth 2900 fathoms.

Genus 449. Gamospyris,^[67] Haeckel, 1881, Prodromus, p. 441.

Definition.—Zygospyrida with two simple lateral feet, forming a ring by union.

The genus Gamospyris and the similar Stephanospyris differ from all other Spyroidea in the possession of a large basal ring, placed in the frontal plane of the shell. This ring has been produced by concrescence of the distal ends of the two large curved lateral feet of Dipospyris.

1. Gamospyris circulus, n. sp. (Pl. 83, fig. 19).

Shell subspherical, tuberculate, with subregular circular pores. Basal plate with four larger collar pores. Apical horn pyramidal, about as long as the shell. The connected feet form together a circular or nearly circular smooth ring, the diameter of which is three to four times as great as that of the shell.

Dimensions.—Shell 0.08 long, 0.09 broad; diameter of the arm-ring 0.25 to 0.33.

Habitat.—Central Pacific, Station 265, depth 2900 fathoms.

2. Gamospyris annulus, n. sp.

Shell nut-shaped, tuberculate, with subregular circular pores. Basal plate with four large central and a circle of eight to twelve small peripheral pores. Apical horn conical, twice as long as the shell. The connected arms form together an elliptical smooth ring, which is five times as long and three times as broad as the shell.

Dimensions.—Shell 0.07 long, 0.09 broad; ring 0.33 long, 0.26 broad.

Habitat.—Central Pacific, Station 268, depth 2900 fathoms.

Genus 450. Stephanospyris,^[68] Haeckel, 1881, Prodromus, p. 441.

Definition.—Zygospyrida with two lateral feet bearing a series of secondary spines and forming a ring by union.

The genus Stephanospyris exhibits the same peculiar armature of the semipinnate lateral feet as its ancestral genus Dorcadospyris, but differs from it in the concrescence of the distal ends of the feet, to form a complete foot-ring. The former therefore bears to the latter the same relation that Gamospyris does to Dipospyris.

1. Stephanospyris cordata, n. sp. (Pl. 85, fig. 10).

Shell subspherical, tuberculate, with small regular circular pores. Basal plate with four larger pores. Apical horn cylindrical, three times as long as the shell, with three to four verticils of teeth. The connected feet form a heart-shaped ring, four times as long and three times as broad as the shell. Each foot bears on the outer convex edge four to six stout conical teeth, shorter than the shell. Distal ends crossed and prominent.

Dimensions.—Shell diameter 0.1; length of the arm-ring 0.4, breadth 0.3.

Habitat.—Central Pacific, Station 265, depth 2900 fathoms.

2. Stephanospyris verticillata, n. sp. (Pl. 85, fig. 11).

Shell nut-shaped, tuberculate, with subregular circular pores. Basal plate with numerous small pores. Apical horn cylindrical, four to six times as long as the shell, with six to ten verticils of teeth. The connected feet form a circular ring, the diameter of which is four times as great as that of the shell. Each foot bears ten to twelve conical teeth, about as long as the shell. Distal ends not crossed and not prominent.

Dimensions.—Diameter of the shell 0.1, of the arm-ring 0.4.

Habitat.—Central Pacific, Station 266, depth 2750 fathoms.

3. Stephanospyris excellens, n. sp. (Pl. 83, fig. 20).

Shell subspherical, tuberculate, with regular circular pores. Basal plate with numerous small pores. Apical horn cylindrical, twice as long as the shell, with eight verticils of teeth. The connected feet form an ovate ring, which is three times as long and two and a half times as broad as the shell. Each foot bears eight conical spinulate teeth, about as long as the shell. The crossed and prominent distal ends bear two parallel vertical teeth.

Dimensions.—Diameter of the shell 0.1, of the arm-ring 0.2 to 0.3.

Habitat.—Central Pacific, Station 268, depth 2900 fathoms.

Subfamily 3. Tetraspyrida, Haeckel, 1881, Prodromus, p. 442.

Definition.—Zygospyrida tetrapoda, with four descending basal feet, two of which are opposite in the sagittal plane (an odd caudal and an odd sternal foot), whilst the two others are paired lateral or pectoral feet.

Genus 451. Tetraspyris,^[69] Haeckel, 1881, Prodromus, p. 442.

Definition.—Zygospyrida with four basal feet crossed in pairs (two sagittal and two lateral). Apex with a horn.

The genus Tetraspyris and the following closely allied Tessarospyris represent together the small subfamily of Tetraspyrida, characterised by the possession of four descending basal feet, three of which correspond to the three original feet of the ancestral genera Cortina and Tripospyris, whilst the fourth in an odd anterior or sternal foot, produced by anterior prolongation of the basilar segment of the sagittal ring. Here, therefore, two opposed feet lie in the sagittal plane (a caudal and a sternal foot), whilst the two others are the paired lateral or pectoral feet, as also in Stephanium and Stephaniscus, p. 965. The Tetraspyrida ought not to be confounded with the Therospyrida (sixth subfamily), in which the four feet have another signification.

Subgenus 1. Tetrarrhabda, Haeckel, 1881, p. 429.

Definition.—Feet simple, not branched nor forked.

1. Tetraspyris stephanium, n. sp. (Pl. 95, fig. 6).

Shell nut-shaped, tuberculate, with deep sagittal stricture and small roundish pores; three pairs of larger pores on each side of the ring. Basal plate with four large collar pores. Apical horn stout conical, half as long as the shell. Two pectoral feet somewhat longer than the two sagittal feet, one and a half times as long as the shell. All four feet straight, three-sided prismatic, strongly divergent.

Dimensions.—Shell 0.08 long, 0.12 broad; horn 0.04 long, feet 0.08 to 0.12 long.

Habitat.—Central Pacific, Station 272, depth 2600 fathoms.

2. Tetraspyris cubica, n. sp.

Shell nearly cubical, smooth, with slight sagittal stricture and small polygonal pores; some larger pores on both sides of the ring. Basal plate with four large collar pores. Apical horn and the four feet of equal size and form, about as long as the shell, cylindrical in the basal, spindle shaped in the distal half.

Dimensions.—Shell 0.09 diameter; horn and feet 0.1 long.

Habitat.—Central Pacific, Station 265, depth 2900 fathoms; also fossil in Barbados.

Subgenus 2. Tetracorethra, Haeckel, 1831, Prodromus, p. 429.

Definition.—Feet branched or forked.

3. Tetraspyris tetracorethra, n. sp. (Pl. 53, figs. 19, 20).

Tetracorethra mirabilis, Haeckel, 1881, Prodromus, p. 439, and Atlas, loc. cit.

Shell campanulate, tuberculate, with deep sagittal stricture and irregular polygonal pores; two pairs of larger pores at the flattened occipital face (fig. 20). Basal plate with four large collar pores. Apical horn very long, thirty to forty times as long as the shell, slender three-sided prismatic, straight, at the distal end irregularly branched, besom-shaped. Four basal feet half as thick as the horn, eight to twelve times as long as the shell, bristle-shaped, irregularly curved and branched, divergent, at the distal end besom-shaped. Central capsule very large; the enclosed small campanulate part sends out through the four collar pores four very long club-shaped basal lobes, half as long as the feet; each lobe contains a large oil-globule (fig. 19).

Dimensions.—Shell 0.036 diameter; horn 1 to 1.5 mm. long, feet 0.3 to 0.4 long.

Habitat.—Central Pacific, Station 270, surface.

4. Tetraspyris calcarata, n. sp.

Shell campanulate, smooth, very similar to that of the preceding species, but differing in the following characters:—the two inferior occipital pores are four times (in the preceding twice) as large as the two superior; the apical horn bears at its distal end only three simple branches; the sternal foot is smaller than the three others, arises higher, is more divergent and curved, and bears at its base a large horizontal conical spur.

Dimensions.—Shell 0.035 diameter; horn 1 to 1.2 long, feet 0.2 to 0.3 long.

Habitat.—Central Pacific, Station 266, surface.

5. Tetraspyris scoparia, n. sp.

Shell campanulate, rough, very similar to the two preceding species, but differing in the following characters:—the four occipital pores are of nearly equal size; the apical horn is simple, not branched; the four feet are forked near the base, so that apparently eight feet diverge, each in the distal half richly branched, besom-shaped.

Dimensions.—Shell 0.038 diameter; horn 1 to 1.1 long, feet 0.4 to 0.5 long.

Habitat.—Central Pacific, Station 268, surface.

Genus 452. Tessarospyris,^[70] Haeckel, 1881, Prodromus, p. 442.

Definition.—Zygospyrida with four basal feet crossed in pairs (two sagittal and two lateral). Apex without horn.

The genus Tessarospyris differs from the preceding Tetraspyris, its ancestral genus, in the absence of the apical horn, and therefore bears to it the same relation that Tristylospyris does to Tripospyris.

1. Tessarospyris clathrobursa, n. sp. (Pl. 53, fig. 8).

Clathrobursa dictyopus, Haeckel, 1881, Prodromus, p. 439, and Atlas, pl. liii. fig. 8.

Shell nearly ovate, strongly compressed, smooth, one and a half times as long as broad, with deep sagittal stricture in the basal half. Pores very small and numerous, irregularly roundish. Basal plate with four very large triangular holes, two larger (posterior) cardinal, and two smaller (anterior) jugular pores; above the latter (on the frontal face) two large mental pores. Two pectoral feet large, half as long as the shell, at the base fenestrated, vertical, and parallel. Two sagittal feet much smaller, nearly horizontal, pyramidal (the caudal larger than the sternal foot). Two longitudinal pectoral ribs arise on the frontal face.

Dimensions.—Shell 0.21 long, 0.14 broad; lateral feet 0.1, sagittal feet 0.02.

Habitat.—South Atlantic, Station 332, depth 2200 fathoms.

2. Tessarospyris nuciformis, n. sp.

Shell nut-shaped, papillate, with deep sagittal stricture. Pores irregular roundish, on both sides of the ring three to six times as large as on the lateral sides. Basal plate with four large pores. Two pectoral feet cylindrical curved, twice as long as the shell and as the two sagittal feet; the caudal is much stronger than the sternal foot.

Dimensions.—Shell 0.06 long, 0.09 broad; lateral feet 0.1, sagittal feet 0.05 long.

Habitat.—Tropical Atlantic, Station 347, depth 2250 fathoms.

3. Tessarospyris seminulum, Haeckel.

Petalospyris seminulum, Stöhr, 1880, Palæontogr., vol. xxvi. pl. iii. fig. 12.

Shell subspherical, smooth, with slight sagittal stricture and small circular pores; some larger pores on both sides of the ring. Basal plate with two large (lateral) pores only. Four feet nearly equal, short, conical, divergent, scarcely one-fourth as long as the shell.

Dimensions.—Shell 0.06 long, 0.08 broad; feet 0.016 long.

Habitat.—Fossil in Tertiary rocks of Sicily (Grotte), Stöhr.

Subfamily 4. Hexaspyrida, Haeckel.

Definition.—Zygospyrida hexapoda, with six descending basal feet; three of these are primary (one odd caudal and two paired pectoral feet), the other three are secondary, opposed diametrically to the former and alternating with them (one odd sternal and two paired tergal feet).

Genus 453. Hexaspyris,^[71] n. gen.

Definition.—Zygospyrida with six basal feet and one apical horn.

The genus Hexaspyris and the two following closely allied genera represent together the peculiar subfamily of Hexaspyrida, and differ from the other Zygospyrida in the possession of six descending basal feet; three of these are the three original, perradial, or primary basal feet of Cortina, Cortiniscus, Plagoniscus, Plectaniscus, Tripospyris, &c.; the other three, usually opposed to the former diametrically, are secondary or interradial; an odd sternal foot (opposed to the odd caudal) and two paired tergal feet (opposed to the two paired pectoral).

Subgenus 1. Hexaspyridium, Haeckel.

Definition.—Feet simple, not branched nor forked.

1. Hexaspyris alterna, n. sp.

Shell nut-shaped, smooth, with deep sagittal stricture and irregular polygonal pores; on each side of the stricture two pairs of larger square annular pores. Basal plate also with four larger collar pores. Apical horn twice as long as the shell, conical. Three primary feet (the apical and the two pectoral) slender, curved, as long as the horn; three secondary feet (the sternal and the two tergal) are half as long as the former and more highly inserted; all six feet strongly divergent, cylindrical, pointed.

Dimensions.—Shell 0.06 long, 0.09 broad; horn 0.15 long, feet 0.08 to 0.14 long.

Habitat.—Central Pacific, Stations 265 to 268, depth 2700 to 2900 fathoms.

2. Hexaspyris setigera, Haeckel.

Ceratospyris setigera, Ehrenberg, 1875, Abhandl. d. k. Akad. d. Wiss. Berlin, p. 66, Taf. xx. fig. 11.

Ceratospyris setigera, Bütschli, 1882, Zeitschr. f. wiss. Zool., vol. xxxvi. p. 539, Taf. xxxii. figs. 11a, 11b.

Shell nut-shaped, tuberculate, with a complete internal sagittal ring and numerous small circular pores. Basal plate with four larger central and a circle of twelve to twenty smaller peripheral pores. Apical horn half as long as the shell, bristle-shaped. Three primary feet longer and more deeply inserted than the three secondary feet; all six feet strongly divergent, bristle-shaped, shorter than the shell.

Dimensions.—Shell 0.06 long, 0.09 broad; horn 0.03 long; primary feet 0.05, secondary 0.02 long.

Habitat.—Fossil in Barbados.

3. Hexaspyris bütschlii, Haeckel.

Ceratospyris triomma, Bütschli (non Ehrenberg), 1882, Zeitschr. f. wiss. Zool., vol. xxxvi. p. 539, Taf. xxxii. fig. 12, a, b.

Shell nut-shaped, spinulate, with a complete internal sagittal ring and subregular circular pores. Basal plate with twelve pores (four larger central and eight smaller peripheral). Apical horn stout, oblique, as long as the shell. Six feet of equal length, slightly divergent, nearly vertical, slender, three to four times as long as the shell.

Dimensions.—Shell 0.05 long, 0.07 broad; horn 0.06, feet 0.15 to 0.2 long.

Habitat.—Fossil in Barbados.

4. Hexaspyris spinosa, Haeckel.

Petalospyris spinosa, Stöhr, 1880, Palæontogr., vol. xxvi. p. 98, Taf. iii. fig. 14.

Shell subspherical, smooth, with slight sagittal stricture and irregular polygonal pores; on each side of the stricture two pairs of larger pores. Basal plate with two large pores only. Apical horn short, pyramidal, three primary feet half as long as the shell and twice as long as the three secondary feet. All six feet pyramidal, slightly divergent.

Dimensions.—Shell 0.05 long, 0.07 broad; horn 0.02, feet 0.02 to 0.04 long.

Habitat.—Fossil in Tertiary rocks of Sicily (Grotte, Caltanisetta).

5. Hexaspyris ophirensis, Haeckel.

Petalospyris ophirensis, Ehrenberg, 1872, Abhandl. d. k. Akad. d. Wiss. Berlin, p. 297, Taf. ix. fig. 24.

Shell nut-shaped, with deep sagittal stricture and numerous irregular roundish pores; two pairs of larger pores on each side of the stricture. Apical horn short, curved. Six feet equal, divergent, straight, slender, about as long as the shell.

Dimensions.—Shell 0.05 long, 0.1 broad; horn 0.01, feet 0.05 to 0.08 long.

Habitat.—Indian Ocean (Zanzibar), depth 2200 fathoms, Pullen.

Subgenus 2. Hexacorethra, Haeckel.

Definition.—Feet forked or branched.

6. Hexaspyris hexacorethra, n. sp. (Pl. 95, fig. 8).

Hexacorethra magica, Haeckel, 1882, Manuscript.

Shell campanulate, smooth, with sharp sagittal stricture and irregular roundish pores. Basal plate with six larger collar pores. Apical horn very long and thin, three-sided prismatic, straight, ten to twenty times as long as the shell, branched at the distal end. Six feet thinner, bristle-shaped, six to eight times as long as the shell, divergent, irregularly curved, in the distal part branched, besom-shaped; the sternal foot at its base with a large conical horizontal spur.

Dimensions.—Shell 0.034 diameter; horn 0.4 to 0.8 long, feet 0.2 to 0.3 long.

Habitat.—Central Pacific, Station 265, surface.

7. Hexaspyris articulata, Haeckel.

Ceratospyris articulata, Ehrenberg, 1875, Abhandl. d. k. Akad. d. Wiss. Berlin, p. 66, Taf. xx. fig. 4.

Shell nut-shaped, tuberculate, with deep sagittal stricture and small irregular roundish pores. Basal plate with six pores (?). Apical horn conical, longer than the shell. Six feet very large, thick cylindrical, divergent, three to four times as long as the shell, with few irregular lateral branches (often much more developed than in Ehrenberg's figure).

Dimensions.—Shell 0.036 long, 0.05 broad; horn 0.05, feet 0.1 to 0.15 long.

Habitat.—Fossil in Barbados.

Genus 454. Liriospyris,^[72] Haeckel, 1881, Prodromus, p. 443.

Definition.—Zygospyrida with six basal feet and three coryphal horns.

The genus Liriospyris differs from the preceding Hexaspyris, its ancestral form, in the possession of three coryphal horns (one odd apical in the middle, and two paired frontal horns on each side of it); it therefore bears to the latter the same relation that Triceraspyris does to Tripospyris.

1. Liriospyris hexapoda, n. sp. (Pl. 86, fig. 7).

Shell subspherical, smooth, with slight sagittal stricture and irregular roundish pores; two to three pairs of large annular pores on each side of the stricture. Basal plate with four large collar pores. Three horns and six feet nearly of the same size and of similar form, conical, divergent, about one-third as long as the shell.

Dimensions.—Shell diameter 0.09 to 0.1; horns and feet 0.03 to 0.04 long.

Habitat.—Central Pacific, Stations 265 to 268, depth 2700 to 2900 fathoms.

2. Liriospyris clathrata, Haeckel.

Dictyospyris clathrus, Ehrenberg, 1854, Mikrogeol., Taf. xxxvi. fig. 25.

Dictyospyris clathrata, Ehrenberg, 1875, Abhandl. d. k. Akad. d. Wiss. Berlin, p. 68, Taf. xix. fig. 7.

Dictyospyris clathrata, Bütschli, 1882, Zeitschr. f. Wiss. Zool., vol. xxxvi. pp. 506, 539; Taf. xxxii. figs. 10a, 10b.

Petalospyris clathrus, Haeckel, 1862, Monogr. d. Radiol., p. 295.

Shell campanulate or nearly spherical, smooth, with slight sagittal stricture. Three pairs of large annular pores on each side of the stricture; a few smaller irregular pores on the lateral sides. Basal plate with six large collar pores (Bütschli, loc. cit., fig. 10a). Three horns and six feet nearly of the same size and form; short, conical, slightly divergent or nearly parallel, shorter than half the ring. (The size of the nine appendages is in this common species rather variable; sometimes they are rudimentary, at other times much stronger than in the good figure of Bütschli.)

Dimensions.—Shell diameter 0.08 to 0.09, horns and feet 0.01 to 0.03.

Habitat.—Cosmopolitan; Mediterranean, Atlantic, Pacific; also fossil in Barbados and Sicily.

3. Liriospyris heteropoda, n. sp.

Shell nut-shaped, nodose, with deep sagittal stricture and small circular pores; two pairs of larger pores on each side of the stricture. Basal plate with four larger central and eight smaller peripheral pores. Apical horn conical, as long as the shell and twice as long as the two curved frontal horns. Three primary feet twice as long as the shell and as the three secondary feet, which are more highly inserted. All six feet slender curved, divergent.

Dimensions.—Shell 0.07 long, 0.11 broad; horn and secondary feet 0.08 long, primary feet 0.15 long.

Habitat.—Western Tropical Pacific, Station 225, depth 4475 fathoms.

4. Liriospyris turrita, Haeckel.

Ceratospyris turrita, Ehrenberg, 1875, Abhandl. d. k. Akad. d. Wiss. Berlin, p. 66, Taf. xx. fig. 1.

Shell ovate, campanulate, smooth, with sharp sagittal stricture and irregular roundish pores; three to four pairs of larger pores on each side of the stricture. Basal plate with four large collar pores. Three horns short and stout, conical, fenestrated at the base. Six feet slender, conical, nearly vertical, of equal size, only one-third as long as the shell.

Dimensions.—Shell 0.08 long, 0.06 broad; horns 0.01 long, feet 0.03 long.

Habitat.—Fossil in Barbados.

5. Liriospyris amphithecta, n. sp. (Pl. 95, fig. 7).

Shell nut-shaped, tuberculate, with distinct sagittal stricture and irregular roundish pores. Basal plate with six larger and twelve smaller pores. Three horns conical, the apical as long as the shell and twice as long as the curved frontal horns. Two pectoral feet cylindrical, very large, curved, divergent, about three times as long as the shell and as the four other feet, which are conical.

Dimensions.—Shell 0.08 long, 0.12 broad; apical horn 0.08, frontal horns 0.05 long; length of the two pectoral feet 0.2, of the four others 0.06.

Habitat.—Central Pacific, Station 266, depth 2750 fathoms.

Genus 455. Cantharospyris,^[73] n. gen.

Definition.—Zygospyrida with six basal feet, without apical horn.

The genus Cantharospyris differs from the preceding two hexapodal genera in the absence of horns on the coryphal face, and has therefore the same relation to them that the hornless Tristylospyris bears to the one-horned Tripospyris and the three-horned Triceraspyris.

1. Cantharospyris carabus, n. sp.

Shell nut-shaped, with deep sagittal stricture and irregular roundish pores. Basal plate with six larger pores. Six feet of different sizes, cylindrical, curved; three primary feet (one caudal and two pectoral) about as long as the shell and twice as long as the three secondary feet.

Dimensions.—Shell 0.08 long, 0.12 broad; feet 0.05 to 0.09 long.

Habitat.—Tropical Atlantic, Station 338, depth 1990 fathoms; Central Pacific, Station 268, depth 2900 fathoms.

2. Cantharospyris ateuchus, Haeckel.

Ceratospyris ateuchus, Ehrenberg, 1875, Abhandl. d. k. Akad. d. Wiss. Berlin, p. 66, Taf. xxi. fig. 4.

Shell nut-shaped, tuberculate, with slight sagittal stricture and unequal circular pores. Basal plate with six larger pores. The two pectoral feet very large and stout, four to six times as long as the shell, widely divergent, curved. The four other feet much smaller and thinner, about as long as the shell.

Dimensions.—Shell 0.06 long, 0.08 broad; length of the two larger feet 0.2 to 0.3, of the four smaller 0.05 to 0.07.

Habitat.—Fossil in Barbados.

3. Cantharospyris radicata, Haeckel.

Ceratospyris radicata, Ehrenberg, 1847, Monatsber. d. k. preuss. Akad. d. Wiss. Berlin, p. 43; Mikrogeol., 1854, Taf. xxii. fig. 37.

Haliomma radicatum, Ehrenberg, 1844, Monatsber. d. k. preuss. Akad. d. Wiss. Berlin, p. 83.

Petalospyris radicata, Haeckel, 1862, Monogr. d. Radiol., p. 295.

Petalospyris radicata, Stöhr, 1880, Palæontogr., vol xxvi. p. 79, Taf. iii. fig. 11.

Shell nut-shaped, smooth, with slight sagittal stricture and irregular roundish pores; two larger pores on each side of the ring. Basal plate with six pores (?). Six feet of equal size and similar form, conical, divergent, slightly curved, shorter than half the ring.

Dimensions.—Shell 0.05 long, 0.08 broad; feet 0.02 long.

Habitat.—Fossil in Barbados and Sicily.

4. Cantharospyris platybursa, n. sp. (Pl. 53, fig. 7).

Platybursa compressa, Haeckel, 1881, Prodromus, p. 429; Atlas, pl. 53, fig. 7.

Shell smooth, nearly discoidal circular, markedly compressed in the sagittal direction, with slight basal stricture. Pores very numerous, irregular polygonal, with thin bars. Basal plate with four very large pores. Six feet short, conical, nearly horizontally expanded. Two sagittal feet (caudal and sternal) larger, about half as long as the shell (shortened in the figure). The two sternal feet larger than the two small or rudimentary tergal feet.

Dimensions.—Shell 0.15 long, 0.13 broad; feet 0.02 to 0.06 long.

Habitat.—Central Pacific, Station 271, depth 2425 fathoms.

Subfamily 5. Pentaspyrida, Haeckel, 1881, Prodromus, p. 442.

Definition.—Zygospyrida pentapoda, with five descending basal feet, one odd caudal foot, and two pairs of lateral feet (two anterior or pectoral, and two posterior or tergal feet).

Genus 456. Clathrospyris,^[74] Haeckel, 1881, Prodromus, p. 442.

Definition.—Zygospyrida with five basal feet and one apical horn.

The genus Clathrospyris and the two following closely allied genera represent together the small subfamily of Pentaspyrida, differing from the other Zygospyrida in the possession of five descending feet on the basal face. Three of these are the primary cortinar feet (of Cortiniscus, Plagoniscus, Tripospyris, &c.), whilst the two others are secondary tergal feet. The Pentaspyrida may therefore be probably derived from the Hexaspyrida by loss of the odd anterior or sternal foot.

1. Clathrospyris camelopardalis, n. sp.

Shell nut-shaped, tuberculate, with deep sagittal stricture. Pores irregular roundish. Basal plate with six pores (?). Two pectoral feet very large, twice as long as the shell, cylindrical, curved. Two tergal feet half as long and thick as the pectoral. Caudal foot and apical horn straight, conical, half as long as the shell.

Dimensions.—Shell 0.07 long, 0.09 broad; horn and odd caudal foot 0.04 long; pectoral feet 0.16, tergal 0.08 long.

Habitat.—South Pacific, Station 297, depth 1775 fathoms.

2. Clathrospyris pyramidalis, n. sp. (Pl. 95, fig. 9).

Shell four-sided pyramidal, truncate, thorny, with a slight sagittal stricture. Pores very large, polygonal roundish. Two pairs of large pores on each side of the ring (at the frontal and the occipital plate). Lateral pores more numerous. Basal plate with four large pores. The four edges of the pyramid are prolonged into four short pyramidal divergent lateral feet (one-third as long as the shell). Caudal foot short. Horn at the apex of the truncate pyramid with two lateral teeth.

Dimensions.—Shell 0.06 long, 0.08 broad; horn and feet 0.02 long.

Habitat.—Central Pacific, Station 272, depth 2600 fathoms.

3. Clathrospyris fusiformis, n. sp.

Shell nearly cubical, smooth, with slight sagittal stricture. Pores roundish; three pairs of larger pores on each side of the ring. Basal plate with six large pores. Five feet of equal length, slender, spindle-shaped, about as long as the shell, divergent. Apical horn conical, and half as long as the feet.