Shell nearly cubical, smooth, without external sagittal stricture. Internal sagittal ring complete. Pores small, roundish; on each side of the ring two crossed pairs of large, square, equal, annular pores. Basal plate also with four longer pores of nearly equal size.

Dimensions.—Shell 0.05 long, 0.07 broad.

Habitat.—Fossil in Barbados.

9. Dictyospyris tetrastoma, Ehrenberg.

Shell nut-shaped, tuberculate, with slight sagittal stricture. Pores numerous, irregular, roundish. No larger annular pores. Basal plate with four large ovate collar pores (the two cardinal twice as large as the two jugular pores).

Dimensions.—Shell 0.05 long, 0.07 broad.

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

10. Dictyospyris spinulosa, Ehrenberg.

Shell nut-shaped, spinulate, without external stricture, with an internal free sagittal ring. Pores numerous, irregular, roundish; on each side of the ring two pairs of very large square pores. Basal plate with four large collar pores.

Dimensions.—Shell 0.07 long, 0.08 broad.

Habitat.—Central Pacific, Stations 271 to 274, depth 2350 to 2750 fathoms; also fossil in Barbados.

11. Dictyospyris mammillaris, n. sp. (Pl. 89, figs. 9, 10).

Shell mammillate, nut-shaped, with deep sagittal stricture. Mammillæ of the surface hemispherical, with a conical apex. Pores not numerous, large, roundish. Two pairs of large pores on each side of the ring. Basal plate with four large pores.

Dimensions.—Shell 0.06 long, 0.08 broad.

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

12. Dictyospyris anthophora, n. sp. (Pl. 89, fig. 8).

Shell tuberculate, nut-shaped, nearly cubical, without external sagittal strictures. Pores not numerous, large, polygonally roundish. Bars between them compressed, elevated, with large, campanulate or flower-like tubercles on the nodal points. Basal plate with four large pores.

Dimensions.—Shell 0.07 long, 0.09 broad.

Habitat.—North Atlantic, Station 349, depth 2450 fathoms.

13. Dictyospyris quadriloba, n. sp.

Shell nut-shaped, smooth, with deep sagittal stricture. Pores numerous, small, circular, on each side of the ring three to four times as large as on the lateral sides. Basal plate with four very large collar pores and a circle of twenty to twenty-five very small peripheral pores.

Dimensions.—Shell 0.08 long, 0.11 broad.

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

14. Dictyospyris messanensis, J. Müller.

Shell nut-shaped, spinulate, with deep sagittal stricture. Pores numerous and small, irregular roundish. No larger annular pores on the sides of the ring. Basal plate with four large, nearly equal, pear-shaped collar pores.

Dimensions.—Shell 0.06 long, 0.08 broad.

Habitat.—Mediterranean; Messina, surface.

Subgenus 4. Dictyospyromma, Haeckel.

Definition.—Basal plate with six or more collar pores.

15. Dictyospyris hexastoma, n. sp.

Shell nut-shaped, tuberculate, with deep sagittal stricture. Pores small, irregular, roundish. Three pairs of larger pores on each side of the ring. Basal plate with six large pores; the middle pair (cardinal) twice as large as the anterior (jugular) and the posterior (cervical).

Dimensions.—Shell 0.08 long, 0.12 broad.

Habitat.—Fossil in Barbados.

16. Dictyospyris enneastoma, n. sp.

Shell ellipsoidal, smooth, without external sagittal stricture, but with an internal free sagittal ring. Pores small and numerous, regular, circular. No larger annular pores. Basal plate with nine pores, three larger interradial alternating with three pairs of adradial.

Dimensions.—Shell 0.07 long, 0.11 broad.

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

17. Dictyospyris polystoma, n. sp.

Shell nut-shaped, mammillate, with distinct sagittal stricture. Pores small and numerous, irregular, on each side of the ring three to five times as large as on the lateral sides. Basal plate with twelve large pores (four central and four alternate pairs of peripheral).

Dimensions.—Shell 0.1 long, 0.14 broad.

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

Family LIII. Tholospyrida, n. fam.

(Pl. 87, figs. 7-10; Pl. 89, figs. 1-4; Pl. 95, figs. 14-16).

Definition.—Spyroidea with a galea, but without thorax; the shell being composed of the bilocular cephalis and of an aboral cupola or galea arising from its coryphal face.

The family Tholospyrida differs from the preceding Zygospyrida, its ancestral group, in the development of a galea, i.e., a fenestrated hemispherical or dome-shaped cupola, which covers the upper face of the cephalis like a cap.

Only three species of this family have been hitherto described: Pylospyris (or Spyridobotrys) trinacria, figured in my Monograph (1862), Pylospyris (or Lithopera) denticulata, figured by Ehrenberg (1872), and Lophospyris (or Ceratospyris) acuminata, figured by Hertwig (1879). Fourteen new species have been found in the collection of the Challenger, which we dispose here among five genera. These may be derived from corresponding genera of Zygospyrida by the development of a galea.

The number and disposition of the terminal feet around the basal plate do not vary so much in the Tholospyrida as in the Zygospyrida. We find here only one genus with three feet, Tholospyris (corresponding to Tripospyris); one genus with two lateral feet, Lophospyris (corresponding to Dipospyris); and two genera with numerous feet, the horned Sepalospyris and the hornless Tiarospyris (the former corresponding to Petalospyris, the latter to Gorgospyris). The fifth genus (Pylospyris) has no feet at all, and may be derived from Circospyris among the Zygospyrida.

The cephalis exhibits in the Tholospyrida the same typical structure which we have described above of all Spyroidea (compare p. 1017). The cupola or galea, arising from its upper face, seems to be a secondary production, perhaps caused by an apical growth of the central capsule, or in other cases by descending branches of the apical horn, which cover the apical face of the calymma with protecting network.

Synopsis of the Genera of Tholospyrida.

Genus 469. Tholospyris,^[87] Haeckel, 1881, Prodromus, p. 441.

Definition.—Tholospyrida with three basal feet and an apical horn.

The genus Tholospyris is probably the common ancestral form of the Tholospyrida, and has arisen from Tripospyris by development of a galea or cupola; this is composed of the apical horn, the lateral branches of which become connected with lateral spines arising from the coryphal face of the cephalis, and of lattice-work developed between the former and the latter. The three descending feet of the basal face are the typical cortinar feet (one odd caudal and two paired pectoral), the same as in the old ancestral genera Cortina, Plagoniscus, Tripospyris, &c.

Subgenus 1. Tholospyrium, Haeckel.

Definition.—Basal feet simple, neither forked nor branched.

1. Tholospyris tripodiscus, n. sp. (Pl. 89, fig. 1).

Shell campanulate, smooth, as broad as long, with deep sagittal stricture. Cephalis compressed, with irregular roundish pores; two or three pairs of larger annular pores on each side of the ring. Basal plate with four large pores. Galea with two very large opposite holes (an occipital and a frontal opening). A slender free perpendicular columella connects the uppermost part of the sagittal ring with the strong three-sided pyramidal apical horn. All three feet of equal length, half as long as the ring, three-sided, prismatic, divergent, with three dentated edges.

Dimensions.—Shell 0.13 diameter, ring 0.08 long, feet 0.05 long.

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

2. Tholospyris fenestrata, n. sp. (Pl. 89, fig. 2).

Shell roundish polyhedral, smooth, with slight sagittal stricture. Cephalis nearly cubical, with irregularly roundish pores; two or three pairs of larger pores on each side of the ring. Basal plate with two very large pores. Galea pyramidal, with two large occipital holes. Columella enclosed in the dorsal wall of the galea, prolonged into an oblique pyramidal spine of the same length. Two pectoral feet pyramidal, nearly vertical and as long as the ring, twice as long as the caudal foot.

Dimensions.—Shell 0.12 diameter, ring 0.07, pectoral feet 0.05 long.

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

3. Tholospyris galeata, n. sp.

Shell helmet-shaped, thorny, with deep sagittal stricture. Cephalis campanulate, with subregular circular pores. Basal plate with three large pores. Galea hemispherical, separated from the cephalis by a sharp horizontal stricture; pores smaller. A slender free columella connects the apex of the ring with the strong conical apical horn, which is half as long as the ring. All three feet of equal length, divergent conical, as long as the horn.

Dimensions.—Shell 0.14 diameter, ring 0.09 long, feet 0.08 long.

Habitat.—Central Pacific, Station 263, depth 2650 fathoms.

Subgenus 2. Tholospyridium, Haeckel.

Definition.—Basal feet forked or branched.

4. Tholospyris ramosa, n. sp. (Pl. 89, fig. 3).

Shell helmet-shaped, smooth, with deep sagittal stricture. Cephalis nearly spherical, with irregularly polygonal pores; four or five pairs of larger annular pores on each side of the strong angular ring. Cupola flat, conical, with two pairs of larger pores. Columella enclosed in its dorsal wall, bearing an irregularly branched horn. Caudal foot short conical, simple. Two pectoral feet half as long as the shell, angular, subvertical, irregularly branched.

Dimensions.—Shell 0.15 diameter, ring 0.1 long, pectoral feet 0.07 long.

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

5. Tholospyris cupola, n. sp. (Pl. 89, fig. 4).

Shell pear-shaped or cupola-shaped, smooth, with slight sagittal stricture. Cephalis not distinctly separated from the galea, as the ring in the uppermost part of the shell-wall becomes obliterated. Pores irregularly polygonal, small and numerous. Basal plate with four large pores. Apical horn and the three divergent feet, irregularly branched; feet nearly as long as the shell, about four times as long as the horn.

Dimensions.—Shell 0.14 diameter, ring 0.1 long, feet 0.12 long.

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

Genus 470. Lophospyris,^[88] Haeckel, 1881, Prodromus, p. 443 (sensu emendato).

Definition.—Tholospyrida with two lateral basal feet and an apical horn.

The genus Lophospyris differs from the preceding Tholospyris, its probable ancestral form, in the absence of the caudal foot, and therefore bears to it the same relation that Dipospyris does to Tripospyris. The two pectoral feet are alone developed and are placed opposite in the frontal plane. Lophospyris may also be derived from Dipospyris by the formation of a galea.

1. Lophospyris dipodiscus, n. sp. (Pl. 95, fig. 14).

Shell ovate, spinulate, with sharp transverse coronal constriction. Cupola hemispherical, half as large as the nut-shaped cephalis. Pores irregularly roundish, much larger on the sagittal constriction. Apical horn pyramidal, about half as long as the shell. Two lateral feet cylindrical, strongly curved, about as long as the shell, with some irregular branches; together forming a nearly complete circle.

Dimensions.—Shell 0.09 long, 0.08 broad; ring 0.04 long, feet 0.08 long.

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

2. Lophospyris acuminata, Haeckel.

Shell campanulate, smooth, without external transverse stricture. Cupola conical, half as long and broad as the nut-shaped cephalis. Pores irregularly roundish, on each side of the sagittal strictures much larger. Basal plate with four large triangular pores. Apical horn slender, prismatic; its outer free part of the same length as the inner columella, and as the two lateral feet, which are curved, shorter than half the ring.

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

Habitat.—Mediterranean, Messina (R. Hertwig).

3. Lophospyris comosa, n. sp.

Shell ovate, spiny, with deep transverse stricture. Cupola large, campanulate, nearly as long and two-thirds as broad as the nut-shaped cephalis. Pores irregular, roundish, of little different size, Basal plate with numerous (eight to twelve) similar pores. Apical horn large, nearly as long as the shell, surrounded by a bunch of smaller divergent spines. Two lateral feet divergent, larger than the shell, cylindrical; at the distal end irregularly branched, at the base surrounded by some smaller spines.

Dimensions.—Shell 0.15 long, 0.11 broad; ring 0.08 long; feet 0.2 long.

Habitat.—Western Tropical Pacific, Station 206, depth 2100 fathoms.

Genus 471. Sepalospyris,^[89] Haeckel, 1881, Prodromus, p. 443.

Definition.—Tholospyrida with numerous basal feet (eight to twelve or more). Galea with a horn.

The genus Sepalospyris has been derived from the similar Petalospyris by development of a galea or cupola on the coryphal face of the cephalis, or from Tholospyris by multiplication of the basal feet. The latter (in the two observed species from twelve to twenty-five) form a regular corona around the basal plate.

1. Sepalospyris platyphylla, n. sp. Pl. 95, fig. 15.

Shell ovate, rough, with sharp transverse stricture. Cupola with delicate network, hemispherical, about two-thirds as long and broad as the nut-shaped thorax. Pores of the latter irregular, roundish; two or three pairs of large pores on each side of the sagittal stricture. Apical horn conical, half as long as the shell. Basal coronet with twelve to fifteen broad, lamellar, truncate, vertical feet, somewhat shorter than the cephalis.

Dimensions.—Shell 0.12 long, 0.13 broad; ring 0.06 long; horn 0.04; feet 0.05 long.

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

2. Sepalospyris polyphylla, n. sp.

Shell campanulate, rough, with deep transverse stricture. Cupola hemispherical, about one-third as long and broad as the nut-shaped thorax. Pores irregular, roundish, a little different in size. Apical horn pyramidal, about as long an the shell. Basal coronet with twenty to twenty-five slender, lamellar, pointed, vertical feet, longer than the shell.

Dimensions.—Shell 0.11 long, 0.12 broad; ring 0.07 long; horn 0.1; feet 0.12 to 0.18 long.

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

Genus 472. Tiarospyris,^[90] Haeckel, 1881, Prodromus, p. 443.

Definition.—Tholospyrida with numerous basal feet (eight to twelve or more). Galea without a horn.

The genus Tiarospyris has probably been derived from the preceding Sepalospyris by reduction and loss of the free apical horn; it therefore bears to it the same relation that the similar Gorgospyris does to Petalospyris.

1. Tiarospyris pervia, n. sp. (Pl. 87, fig. 7).

Shell nut-shaped, smooth, with deep sagittal stricture. Cephalis on the lateral sides with numerous small roundish pores, on each side of the ring with a pair of very large holes. Basal plate with two large collar pores. Cupola flat, cap-shaped, with two large parietal pores above the ring. Coronet with eight conical, slightly divergent feet, about one-fourth as long as the shell.

Dimensions.—Shell 0.08 long, 0.1 broad; ring 0.06 long; feet 0.02 long.

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

2. Tiarospyris galea, n. sp.

Shell helmet-shaped, with deep sagittal stricture. Cephalis with irregular, polygonal pores; on each side of the ring two pairs of larger annular pores. Basal plate with four large pores. Cupola high, conical, nearly as long as the cephalis, separated from it by a distinct coronal stricture. Basal coronet with twelve to sixteen slender curved divergent feet, nearly as long as the shell.

Dimensions.—Shell 0.16 long, 0.12 broad; ring 0.1 long; feet 0.15 long.

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

3. Tiarospyris mitra, n. sp. (Pl. 87, figs. 9, 10).

Shell subspherical, smooth. Cephalis on the lateral sides with small roundish, double-contoured pores, on each side of the ring with three to five pairs of larger pores, each of which is closed by a thin fenestrated lamella (different on the frontal face, fig. 9, and the dorsal face, fig. 10). Cupola flat, cap-shaped, separated by a distinct coronal stricture, with similar pores. Basal coronet with, ten to twelve short conical convergent feet.

Dimensions.—Shell 0.11 long, 0.12 broad; ring 0.04 long; feet 0.02 long.

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

4. Tiarospyris amphora, n. sp. (Pl. 87, fig. 8).

Shell amphora-shaped, in the upper half smooth, in the lower spiny, without external sagittal stricture. Cephalis subspherical with a small number of irregular, large, roundish pores, which are closed by a thin fenestrated lamella. Cupola flat, cap-shaped, with numerous small pores. Base covered with numerous conical divergent feet of different sizes, the largest one-third as long as the shell. Internal sagittal ring ovate, nearly free.

Dimensions.—Shell 0.14 long, 0.13 broad; ring 0.1 long; feet 0.04 long.

Habitat.—South Pacific, Station 285, depth 2375 fathoms.

Genus 473. Pylospyris,^[91] Haeckel, 1881 Prodromus, p. 443.

Definition.—Tholospyrida without basal feet, with an apical horn.

The genus Pylospyris was first known from a Mediterranean species, called by me, in 1862, Spyridobotrys trinacria. As this name was given erroneously, on the supposition of a near relation to the Botryodea (= Polycyrtida), I changed it afterwards to Pylospyris. This genus differs from the other Tholospyrida in the total absence of basal feet, and may therefore be derived either from them by reduction of the feet, or from Dictyospyris by formation of a galea.

1. Pylospyris denticulata, Haeckel.

Shell spinulate, with slight coronal and deep sagittal constriction, with irregular, roundish pores of variable size. Galea hemispherical, about half as long and broad as the nut-shaped cephalis. No symmetrically disposed larger pores.

Dimensions.—Galea 0.04 long, 0.06 broad; cephalis 0.08 long, 0.1 broad.

Habitat.—Antarctic Ocean, Ehrenberg. (Included in the ice.)

2. Pylospyris trinacria, Haeckel.

Shell tuberculate, with sharp coronal and sagittal stricture. Galea campanulate, with very small circular pores, and a short conical apical horn of the same length. Cephalis nut-shaped, with large, irregular, roundish pores; two pairs of larger annular pores on each side of the sagittal ring, also four larger pores in the basal plate.

Dimensions.—Galea 0.03 long, 0.04 broad; cephalis 0.04 long, 0.07 broad.

Habitat.—Mediterranean, Messina, surface.

3. Pylospyris canariensis, n. sp. (Pl. 95, fig. 16).

Shell rough, with deep coronal and slight sagittal constriction. Galea hemispherical, with numerous small irregular, roundish pores, about half as long as the cephalis, with a slender conical horn of twice the length. Cephalis nut-shaped, with larger roundish pores of very unequal size, three pairs of larger pores on each side of the ring. Basal plate with two larger pores.

Dimensions.—Galea 0.03 long, 0.08 broad; cephalis 0.06 long, 0.11 broad.

Habitat.—North Atlantic, Canary Islands, surface.

Family LIV. Phormospyrida, Haeckel (sensu emendato) (Pl. 83, figs. 13-15; Pl. 95, figs. 17-19).

Definition.—Spyroidea with a thorax, without galea; the shell composed of the bilocular cephalis and of a simple thorax arising from its basal face.

The family Phormospyrida differs from the Zygospyrida, their ancestral group, in the development of a thorax, or a second fenestrated shell-joint, which arises from the lower face of the cephalis. It corresponds, therefore, to the Dicyrtida among the Cyrtoidea, and may perhaps be, wholly or partially, the ancestral group of the latter. When the sagittal ring and the longitudinal constriction of the cephalis disappear, the Phormospyrida pass over into the Dicyrtida.

Only three species of this family have been hitherto known, which were found fossil in Barbados, and described by Ehrenberg (1875) as Lithobotrys stiligera and Petalospyris confluens, and by Bütschli (1882) as Petalospyris anthocyrtoides. Fifteen other species are found in the Challenger collection, which we dispose here among five genera.

Two of these five genera (the horned Acrospyris and the hornless Phormospyris) possess the three typical basal feet of Cortina and Tripospyris, and may be derived from these genera by the development of network between the bases of the feet. The three other genera possess numerous feet, and may be derived in the same way from the Polyspyrida; the apical face differs in the three genera, in Desmospyris it is hornless, in Patagospyris it bears an apical horn, and in Rhodospyris three horns (an apical and two lateral or frontal).

The cephalis in the Phormospyrida exhibits the same typical structure, which we have described above, of all Spyroidea (compare, p. 1017). The thorax or the second joint of the shell arises by reticular connection of the bases of the basal feet, and represents a cylindrical or truncate-conical joint in the polypodal forms, or a three-sided joint in the tripodal forms. The terminal aperture or the mouth of the thorax is constantly open, and surrounded by the free ends of the feet.

Subfamily 1. Acrospyrida, Haeckel, 1881, Prodromus, p. 441 (sensu emendato).

Definition.—Phormospyrida with three basal feet (an odd caudal and two paired pectoral).

Genus 474. Acrospyris,^[92] Haeckel, 1881, Prodromus, p. 441.

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

The genus Acrospyris is probably the oldest and most primitive among the Phormospyrida, perhaps the original ancestral form of this family. It has been derived from Tripospyris by the development of lattice-work between the three basal feet, forming a second joint or thorax. It has also therefore a close relation to the simplest forms of the triradiate Dicyrtida: Dictyophimus, Clathrocanium, &c. It differs from these in the distinct sagittal constriction of the cephalis, which divides it into two lateral loculi.

1. Acrospyris clathrocanium, n. sp. (Pl. 95, fig. 17).

Shell tuberculate, with distinct collar and deep sagittal stricture. Cephalis nut-shaped, with numerous irregular, roundish pores; three pairs of larger annular pores on each side of the ring. Basal plate with four larger pores (two major cardinal and two minor jugular pores). Apical horn slender, pyramidal, curved, about as long as the shell, with three recurved short spines. Thorax three-sided, about twice as large as the cephalis, with three large basal holes and a broad riband with numerous smaller holes; three ribs between them stout, pyramidal, strongly curved, prolonged into three convergent crescentic feet.

Dimensions.—Cephalis 0.08 long, 0.11 broad; thorax 0.14 long, 0.16 broad.

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

2. Acrospyris dictyophimus, n. sp.

Shell smooth. Cephalis and thorax of nearly the same structure and form as in the preceding species; it differs from the latter in the shape of the three stout basal feet, which are straight, much longer than the thorax, divergent, and at the broader base irregularly fenestrated, without three larger holes.

Dimensions.—Cephalis 0.05 long, 0.08 broad; thorax 0.07 long, 0.12 broad.

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

3. Acrospyris pyramidalis, n. sp.

Shell three-sided pyramidal, with slight collar stricture. Cephalis campanulate, with deep sagittal stricture and stout ring, armed with a strong pyramidal horn of the same length. Thorax shorter and broader, truncate. Pores irregular, roundish, scarce. Three feet divergent, three-sided pyramidal, as long as the cephalis.

Dimensions.—Cephalis 0.05 long, 0.06 broad; thorax 0.02 long, 0.08 broad.

Habitat.—Fossil in Barbados.

4. Acrospyris macrocephala, n. sp.

Shell spinulate, with deep sagittal and very deep collar stricture. Cephalis very large, nut-shaped, twice as long and broad as the small, truncate, pyramidal thorax. Pores irregular, roundish. Horn spindle-shaped, nearly as long as the cephalis; the three divergent feet are of the same form and size as the horn, and arise as three ribs from the deep collar stricture.

Dimensions.—Cephalis 0.1 long, 0.15 broad; thorax 0.05 long, 0.09 broad.

Habitat.—Fossil in Barbados.

5. Acrospyris fragilis, n. sp.

Shell very thin-walled and fragile, with deep sagittal and collar strictures. Pores very small and numerous, circular. Cephalis nut-shaped, nearly spherical, with a slender bristle-shaped horn of the same length. Basal stricture with two large collar pores only (luminella). Thorax nearly three-sided prismatic, longer than the cephalis, with three parallel ribs, prolonged into three slender, long, bristle-shaped feet.

Dimensions.—Cephalis 0.05 long, 0.06 broad; thorax 0.08 long, 0.06 broad.

Habitat.—North Pacific, Station 244, surface.

Genus 475. Phormospyris,^[93] Haeckel, 1881, Prodromus, p. 442 (sensu emendato).

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

The genus Phormospyris has been derived from Acrospyris, its ancestral form, by reduction and loss of the apical horn; it therefore bears to the latter the same relation that Tristylospyris has to the ancestral Tripospyris.

1. Phormospyris tricostata, n. sp. (Pl. 83, fig. 15).

Cephalis nut-shaped, thorny, with deep sagittal and collar strictures, half as large as the pyramidal thorax. Mouth of the latter dilated and ciliated, twice as broad as the cephalis. Pores irregular, polygonal, with thin bars. Three cylindrical, straight, divergent ribs descend in the wall of the thorax, and are prolonged over the mouth into three short conical teeth.

Dimensions.—Cephalis 0.06 long, 0.09 broad; thorns 0.08 long, 0.16 broad.

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

2. Phormospyris tridentata, n. sp. (Pl. 95, fig. 18).

Cephalis nut-shaped, with deep sagittal and collar strictures, about twice as large as the thorax. Mouth of the latter half as broad as the cephalis. Pores very small and numerous, subregular, circular. Collar plate with four large triangular pores. In the wall of the thorax three vertical prismatic ribs descend, which are prolonged over the mouth into three parallel feet of the same length.

Dimensions.—Cephalis 0.06 long, 0.08 broad; thorns 0.04 long, 0.06 broad.

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

3. Phormospyris trifoliata, n. sp.

Cephalis nut-shaped, with deep sagittal and collar strictures, smaller than the thorax. Mouth of the latter nearly as broad as the cephalis. Pores circular, double-contoured, larger in the thorax than in the cephalis. The thorax has no lateral ribs, but bears around the mouth three large triangular lamellar terminal feet.

Dimensions.—Cephalis 0.04 long, 0.05 broad; thorax 0.06 long, 0.05 broad.

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

Subfamily 2. Rhodospyrida, Haeckel.

Definition.—Phormospyrida with a corona of numerous (nine to twelve or more) basal feet.

Genus 476. Patagospyris,^[94] Haeckel, 1881, Prodromus, p. 443.

Definition.—Phormospyrida with numerous basal feet (nine to twelve or more) and an apical horn.

The genus Patagospyris and the two following closely allied genera differ from the two preceding tripodal genera in the multiplication of the basal feet, and therefore have to the latter the same relation that the Polyspyrida (Petalospyris) bear to the Tripospyrida (Tripospyris). When the numerous basal feet of Petalospyris become connected by lattice-work, Patagospyris arises.