Shell spiny, with sharp collar stricture. Length of the two joints = 1 : 2, breadth = 1 : 3. Cephalis hemispherical, with a conical horn of the same length and some accessory spines. Thorax campanulate, with subregular, circular pores. Mouth little constricted, with twenty to thirty small, triangular, convergent feet, about as long as the cephalis. (In Ehrenberg's incomplete figure they are mostly broken off.)

Dimensions.—Cephalis 0.02 long, 0.02 broad; thorax 0.04 long, 0.06 broad.

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

15. Anthocyrtium ehrenbergii, Haeckel.

Shell smooth, with obliterated collar stricture. Length of the two joints = 3 : 10, breadth = 2 : 8. Cephalis subcylindrical, with an excentric, stout, pyramidal horn of the same length. Thorax bottle-shaped, with small, regular, circular pores of equal size. Mouth little constricted, with twenty to thirty small, triangular, convergent feet, about half as long as the cephalis.

Dimensions.—Cephalis 0.03 long, 0.02 broad; thorax 0.1 long, 0.08 broad.

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

16. Anthocyrtium zanguebaricum, Haeckel.

Shell smooth, with slight collar stricture. Length of the two joints = 3 : 10, breadth = 2 : 7. Cephalis subspherical, with an excentric conical horn of the same length. Thorax slender, ovate or bottle-shaped, with irregular, roundish pores increasing in size downwards. Mouth little constricted, with twelve to fifteen small, triangular, convergent feet, about half as long as the cephalis.

Dimensions.—Cephalis 0.03 long, 0.02 broad; thorax 0.1 long, 0.07 broad.

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

17. Anthocyrtium ficus, Haeckel.

Shell rough, with obliterated collar stricture. Length of the two joints = 2 : 12, breadth = 3 : 10. Cephalis conical, with a large, cylindrical horn, pyramidal at the base, about as long as the thorax. Thorax subovate, truncate, papillate, with small, regular, circular, quincuncial pores of the same breadth as the bars. Mouth constricted, two-thirds as broad as the thorax, with fifteen to twenty strongly convergent, lamellar, rectangular or sword-shaped feet, nearly as long as the thorax.

Dimensions.—Cephalis 0.02 long, 0.03 broad; thorax 0.12 long, 0.1 broad.

Habitat.—Fossil in Barbados.

18. Anthocyrtium flosculus, n. sp. (Pl. 62, fig. 19).

Shell ribbed, with distinct collar stricture. Length of the two joints = 1 : 4, breadth = 2 : 4. Cephalis hemispherical, with small, circular pores and a large cylindrical horn, twice as long as the thorax and half as broad at the base as the cephalis. Thorax subovate, truncate, with twenty-four to thirty longitudinal ribs and alternating rows of circular pores. Mouth constricted, two-thirds as broad as the thorax, with twenty-four to thirty slender, convergent feet, which are as long as the entire shell, with their edges in close contact and their distal ends pointed.

Dimensions.—Cephalis 0.03 long, 0.05 broad; thorax 0.12 long, 0.12 broad.

Habitat.—Central Pacific, Stations 265 to 274, depth 2350 to 2925 fathoms.

Genus 568. Anthocyrtidium,^[185] Haeckel, 1881, Prodromus, p. 431.

Definition.—Sethophormida, (vel Dicyrtida multiradiata aperta) without thoracic ribs, with numerous (twelve to fifteen or more) subterminal feet, which are separated from the constricted mouth by a ring of lattice-work. Cephalis free, with an apical horn.

The genus Anthocyrtidium has been derived from the preceding Anthocyrtium by further growth and constriction of the peristome, which becomes separated from the subterminal corona of feet by a more or less broad ring of lattice-work.

1. Anthocyrtidium cineraria, n. sp. (Pl. 62, fig. 16).

Shell campanulate, smooth, with obliterated collar stricture. Length of the two joints = 5 : 11, breadth = 3 : 13. Cephalis subcylindrical-ovate, with a conical straight horn of half the length. Thorax hemispherical, inflated, nearly twice as broad as the constricted mouth. Pores subregular, circular, double-contoured. Above the mouth, separated from it by two rows of pores, a corona of twelve to fifteen short conical feet, which are directed downwards, slightly curved, and as long as the cephalic horn.

Dimensions.—Cephalis 0.05 long, 0.03 broad; thorax 0.11 long, 0.13 broad.

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

2. Anthocyrtidium ligularia, n. sp. (Pl. 62, fig. 15).

Shell campanulate, rough, with distinct collar stricture. Length of the two joints = 1 : 4, breadth = 2 : 6. Cephalis hemispherical, with a slender, conical, slightly curved horn, about as long as the shell. Thorax hemispherical, three times as broad as the cephalis, nearly twice as broad as the constricted mouth, which is prolonged into a prominent smooth ring. Above the mouth, separated from it by one row of pores, a corona of twelve to fifteen slender linear feet, which are slightly curved, divergent, and emarginate at the truncated distal end.

Dimensions.—Cephalis 0.015 long, 0.03 broad; thorax 0.06 long, 0.09 broad.

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

3. Anthocyrtidium matricaria, n. sp.

Shell campanulate, rough, very similar to the preceding species, but differing in the straight, large, pyramidal horn of the cephalis (as long as the shell), and in the longer feet, which are twelve to fifteen in number, little curved at the distal end, pointed, and about as long as the shell. Length of the two joints = 2 : 6, breadth = 3 : 8. Differs from the similar Anthocyrtium centaurea, Ehrenberg (1875, loc. cit., Taf. vi. fig. 5), mainly in the prominent ring of the peristome.

Dimensions.—Cephalis 0.02 long, 0.03 broad; thorax 0.06 long, 0.08 broad.

Habitat.—Fossil in Barbados.

Genus 569. Carpocanium,^[186] Ehrenberg, 1847, Monatsber. d. k. preuss. Akad. d. Wiss. Berlin, p. 54.

Definition.—Sethophormida (vel Dicyrtida multiradiata aperta) without thoracic ribs, with numerous terminal feet around the mouth (six to twelve or more). Cephalis hidden in the thorax, without apical horn.

The genus Carpocanium, very common, and rich in numerous living and fossil species, was formerly placed by me among the true Monocyrtida, since an external constriction is not visible (Monogr., 1862, p. 290). Afterwards (in 1879) Richard Hertwig demonstrated that the cavity of the ovate shell, externally simple, is divided by an internal transverse septum into two joints, the upper of which is the flat rudimentary cephalis (Organism. d. Radiol., p. 79; compare also Bütschli, 1882, loc. cit., p. 535). Indeed this septum, with four central crossed cortinar beams, is a true collar septum, and Carpocanium has been derived from Anthocyrtis or Desmospyris by reduction of the cephalis, which is very flat and perfectly hidden in the uppermost part of the thorax. The apical horn is lost. If the internal septum were to become lost, the genus would pass over into Carpocanistrum.

Subgenus 1. Carpocanarium, Haeckel.

Definition.—Peristome-corona composed of six feet (three primary perradial alternating with three secondary interradial).

1. Carpocanium calycodes, Stöhr.

Shell urceolate, smooth, nearly twice as long as broad, with hemispherical vaulted cephalis. Length of the two joints = 3 : 16, breadth = 5 : 10. Pores regular, circular, as broad as the bars, quincuncially disposed in about five longitudinal series at each side. Mouth constricted, half as broad as the thorax. Peristome with six vertical, equilateral, triangular feet.

Dimensions.—Cephalis 0.015 long, 0.025 broad; thorax 0.08 long, 0.05 broad.

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

2. Carpocanium setosum, Haeckel.

Shell ovate, truncate at the mouth, thorny, exactly as long as broad. Length of the two joints = 1 : 8, breadth = 3 : 9. Cephalis hidden, with very small pores. Thorax inflated, with regular, circular pores, twice as broad as the bars, in about ten longitudinal series at each side. Mouth constricted, half as broad as the thorax. Peristome with six vertical, parallel, broad, lamellar, rectangular feet, separated by equal internals, half as long as the shell.

Dimensions.—Cephalis 0.01 long, 0.03 broad; thorax 0.08 long, 0.09 broad.

Habitat.—Fossil in Barbados.

3. Carpocanium laeve, Ehrenberg.

Shell subspherical, smooth, equal in length and breadth, with little vaulted, cap-shaped cephalis. Length of the two joints = 1 : 6, breadth = 4 : 7. Pores regular, circular, twice as broad as the bars, in nine longitudinal rows. Mouth constricted, only one-third as broad as the thorax. Peristome with six strong conical feet, which are slightly curved and convergent.

Dimensions.—Cephalis 0.01 long, 0.04 broad; thorax 0.06 long, 0.07 broad.

Habitat.—Mediterranean (Greece); Tropical Atlantic, Station 348, depth 2450 fathoms.

4. Carpocanium lanceolatum, n. sp.

Shell subspherical, thorny, with perfectly hidden cephalis. Length of the two joints = 1 : 3, breadth = 1 : 3. Pores regular, circular, hexagonally framed, half as broad as the bars, in about sixteen longitudinal rows at each side. Mouth constricted, half as broad as the thorax. Peristome with six large lanceolate, vertical, lamellar feet, half as long as the shell.

Dimensions.—Cephalis 0.03 long, 0.03 broad; thorax 0.09 long, 0.09 broad.

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

Subgenus 2. Carpocanidium, Haeckel.

Definition.—Peristome-corona composed of nine feet (three primary perradial and six secondary interradial).

5. Carpocanium diadema, Haeckel.

Shell ovate, with little vaulted cephalis. Length of the two joints = 1 : 8, breadth = 3 : 6. Pores regular, circular, in about twelve longitudinal rows, twice as broad as the bars. Mouth constricted, half as broad as the thorax. Peristome with nine vertical, equilateral, triangular feet.

Dimensions.—Cephalis 0.01 long, 0.03 broad; thorax 0.08 long, 0.06 broad.

Habitat.—Cosmopolitan; Mediterranean, Atlantic, Indian, Pacific; many stations, surface.

6. Carpocanium cylindricum, n. sp.

Shell cylindrical, with hemispherical, flatly vaulted cephalis. Length of the two joints = 1 : 4, breadth = 3 : 3. Pores regular, circular, double-contoured, as broad as the bars, in about fifteen longitudinal series. Mouth constricted, two-thirds as broad as the thorax. Peristome with nine vertical, slender, triangular, pointed feet.

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

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

7. Carpocanium enneaphyllum, n. sp.

Shell slenderly ovate, at the mouth truncate, thorny, with hemispherical, vaulted cephalis. Length of the two joints = 1 : 6, breadth = 2 : 4. Pores regular, circular, hexagonally framed, as broad as the bars, in about thirteen longitudinal rows. Mouth constricted, about two-thirds as broad as the thorax. Peristome with nine broad, lamellar, vertical, nearly square feet, half as long as the shell, with small intervals.

Dimensions.—Cephalis 0.02 long, 0.04 broad; thorax 0.12 long, 0.09 broad.

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

8. Carpocanium solitarium, Ehrenberg.

Shell slenderly ovate, twice as long as broad, with hidden spherical cephalis, completely enclosed in the summit of the thorax. Length of the two joints = 1 : 6, breadth = 1 : 4. Pores small, regular, circular, as broad as the bars, in about eleven longitudinal rows. Mouth gradually constricted, half as broad as the thorax. Peristome with nine ovate blunt feet, which are as long as the cephalis, little curved and convergent.

Dimensions.—Cephalis 0.02 long, 0.02 broad; thorax 0.12 long, 0.07 broad.

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

9. Carpocanium gemmula, n. sp.

Shell subspherical, smooth, equal in length and breadth, with hemispherical vaulted cephalis. Length of the two joints = 2 : 7, breadth = 4 : 9. Pores small, regular, circular, twice as broad as the bars, in about twenty longitudinal rows. Mouth strongly constricted, only one-fourth as broad as the thorax. Peristome with nine conical feet, which are twice as long as the cephalis, curved, and so convergent that their distal ends come nearly in contact.

Dimensions.—Cephalis 0.02 long, 0.04 broad; thorax 0.07 long, 0.09 broad.

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

10. Carpocanium microdon, Ehrenberg.

Shell broad, ovate, rough, with perfectly hidden cephalis. Length of the two joints = 2 : 9, breadth = 4 : 7. Pores very small and scarce, smaller than the bars between them, irregularly scattered. Mouth constricted, one-third as broad as the thorax. Peristome with nine short, triangular, pointed, convergent feet.

Dimensions.—Cephalis 0.02 long, 0.04 broad; thorax 0.09 long, 0.07 broad.

Habitat.—Mediterranean (Crete), Atlantic (Canary Islands), Station 354, surface.

Subgenus 3. Carpocanobium, Haeckel.

Definition.—Peristome-corona composed of twelve or more feet.

11. Carpocanium trepanium, n. sp. (Pl. 52, fig. 18).

Shell subcylindrical, with flatly vaulted cephalis. Length of the two joints = 1 : 6, breadth = 3 : 4. Pores regular, hexagonal, four to six times as broad as the bars. Mouth little constricted, two-thirds as broad as the thorax. Peristome with eighteen to twenty-four large, slender, triangular, vertical feet.

Dimensions.—Cephalis 0.02 long, 0.06 broad; thorax 0.12 long, 0.08 broad.

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

12. Carpocanium hexagonale, n. sp. (Pl. 52, fig. 15).

Shell broadly ovate or subconical, with vaulted, cap-shaped cephalis. Length of the two joints = 2 : 7, breadth = 6 : 9. Thorax subglobular, truncate. Pores subregular, hexagonal, three to four times as broad as the bars. Mouth constricted, two-thirds as broad as the thorax. Peristome with twenty to twenty-five small, triangular, vertical feet.

Dimensions.—Cephalis 0.02 long, 0.05 broad; thorax 0.07 long, 0.09 broad.

Habitat.—Tropical Atlantic, Station 347, surface.

13. Carpocanium petalospyris, n. sp. (Pl. 52, fig. 19).

Shell subspherical, smooth, with perfectly hidden cephalis. Length of the two joints = 1 : 6, breadth = 3 : 6. Pores regular, circular, hexagonally framed, twice as broad as the bars, in about sixteen longitudinal rows. Mouth slightly constricted, little narrower than the thorax. Peristome with twenty to twenty-four vertical, broad, lamellar feet, which are nearly as long as the shell, at the distal end truncate, and almost in contact at their edges.

Dimensions.—Cephalis 0.02 long, 0.05 broad; thorax 0.11 long, 0.12 broad.

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

14. Carpocanium polypterum, Haeckel.

Shell campanulate-conical, smooth, with perfectly hidden cephalis. Length of the two joints = 1 : 6, breadth = 4 : 6. Pores regular, circular, twice as broad as the bars, in about sixteen longitudinal rows. Mouth wide open, not constricted. Peristome with twenty to thirty vertical, slender, conical feet, about as long as the shell.

Dimensions.—Cephalis 0.01 long, 0.04 broad; thorax 0.06 long, 0.06 broad.

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

15. Carpocanium palmipes, n. sp.

Shell ovate, very thick-walled, smooth. Lower half of the subspherical cephalis hidden in the summit of the thorax, upper half free, with few small pores. Length of the two joints = 3 : 10, breadth = 3 : 10. Thorax foveolate, with oblong dimples, each of which encloses a small, circular, double-contoured pore, half as broad as the bars. Mouth little constricted, nearly as broad as the thorax. Peristome prolonged into a solid, cylindrical tube, nearly as long and as broad as the shell; the upper half of the tube is solid, the lower divided into from twelve to fifteen vertical, lamellar, pointed feet.

Dimensions.—Cephalis 0.03 long, 0.03 broad; thorax 0.1 long, 0.1 broad.

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

16. Carpocanium peristomium, n. sp. (Pl. 52, figs. 16, 17).

Shell ovate, smooth, with perfectly hidden, flat cephalis (fig. 17). Length of the two joints = 2 : 10, breadth = 5 : 9. Pores small and very numerous, regular, circular, as broad as the bars, in about twenty longitudinal rows. Mouth little constricted. Peristome broad; in the upper half a hyaline, circular ring, in the lower half divided into from eighteen to twenty-four triangular, curved, little convergent feet.

Dimensions.—Cephalis 0.02 long, 0.05 broad; thorax 0.1 long, 0.09 broad.

Habitat.—Cosmopolitan; Atlantic, Indian, Pacific; many stations, at various depths.

17. Carpocanium coronatum, Ehrenberg.

Shell ovate, smooth, with perfectly hidden, subspherical cephalis. Length of the two joints = 2 : 9, breadth = 2 : 8. Pores small and very numerous, twice as broad as the bars, regular, circular, in about twenty longitudinal rows. Mouth little constricted, two-thirds as broad as the thorax. Peristome with twenty-five to thirty short, bristle-shaped feet, which are slightly curved, convergent, and in the upper half connected by a solid ring.

Dimensions.—Cephalis 0.02 long, 0.02 broad; thorax 0.09 long, 0.08 broad.

Habitat.—Fossil in Barbados.

18. Carpocanium dactylus, n. sp.

Shell slenderly ovate, twice as long as broad, with flat, perfectly hidden cephalis. Length of the two joints = 1 : 12, breadth = 4 : 8. Pores subregular, circular, as broad as the bars, in about twelve longitudinal rows, separated by prominent longitudinal ribs. Mouth constricted, two-thirds as broad as the thorax. Peristome with twelve large, lanceolate, lamellar, convergent feet.

Dimensions.—Cephalis 0.01 long, 0.04 broad; thorax 0.12 long, 0.08 broad.

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

19. Carpocanium irregulare, n. sp. (Pl. 52, fig. 14).

Shell irregular, roundish, subovate, with flat and oblique, perfectly hidden cephalis. Length of the two joints = 1 : 10, breadth = 3 : 9. Pores irregularly scattered, roundish, about as broad as the bars. Mouth wide open, not at all or little constricted. Peristome with twenty to thirty long, lamellar, pointed feet, which are irregularly curved and convergent.

Dimensions.—Cephalis 0.01 to 0.02 long, 0.03 to 0.04 broad; thorax 0.09 to 0.11 long, 0.08 to 0.09 broad.

Habitat.—Central Pacific, Station 263 to 274, surface, and at various depths.

20. Carpocanium verecundum, n. sp. (Pl. 52, figs. 12, 13).

Shell ovate, smooth, with flat, perfectly hidden cephalis (fig. 12). Length of the two joints = 1 : 9, breadth = 4 : 9. Pores subregular, circular, twice as broad as the bars, in about eighteen, partly interrupted, longitudinal rows, separated by prominent crests. Mouth little constricted. Peristome with twenty to twenty-four broad, lamellar, pointed feet, which are about as long as the shell, little curved, and convergent.

Dimensions.—Cephalis 0.01 long, 0.04 broad; thorax 0.09 long, 0.09 broad.

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

21. Carpocanium virgineum, n. sp. (Pl. 52, fig. 20).

Shell ovate, smooth, with flat perfectly hidden cephalis. Length of the two joints = 1 : 8, breadth = 3 : 9. Pores regular, circular, hexagonally framed, as broad as the bars, in about sixteen longitudinal rows on each side. Mouth little constricted. Peristome with eighteen to twenty-four very large, lamellar, pointed feet, which are longer than the shell, and so curved and convergent that their distal points come nearly in contact.

Dimensions.—Cephalis 0.01 long, 0.03 broad; thorax 0.08 long, 0.09 broad.

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

Subfamily 2. Sethophænida, Haeckel, 1881, Prodromus, p. 433.

Definition.—Anthocyrtida with the basal mouth of the shell fenestrated (vel Dicyrtida multiradiata clausa).

Genus 570. Sethophæna,^[187] Haeckel, 1881, Prodromus, p. 433.

Definition.—Sethophænida (vel Dicyrtida multiradiata clausa) with lateral apophyses. Cephalis with a horn.

The genus Sethophæna and the following Clistophæna form together the small subfamily of Sethophænida, comprising those Dicyrtida in which the thorax bears numerous radial appendages (four to six or more), and the mouth is closed by a lattice-plate. In Sethophæna the apophyses are lateral wings, as in Micromelissa, from which it may be derived by development of secondary wings, interpolated between the three primary wings.

1. Sethophæna tetraptera, n. sp.

Shell smooth, with deep collar stricture. Length of the two joints = 3 : 10, breadth = 4 : 9. Cephalis subspherical, without horn. Thorax ovate, with rounded hemispherical base, and subregular, hexagonal pores. From its upper half (below the collar stricture) arise four divergent, conical, straight wings, of half the length, opposite in pairs in two meridional planes, perpendicular to one another (compare Tetralacorys, Pl. 65, figs. 4, 5).

Dimensions.—Cephalis 0.03 long, 0.04 broad; thorax 0.1 long, 0.09 broad.

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

2. Sethophæna hexaptera, n. sp. (Pl. 97, fig. 13).

Shell rough, pear-shaped, with distinct collar stricture. Length of the two joints = 1 : 4, breadth = 2 : 4. Cephalis hemispherical, with a conical horn of the same length. Thorax inflate, inversely ovate, nearly pear-shaped, with subregular, circular pores. From its upper half arise, by a broad base, six divergent, strong, conical wings, which are horn-like, curved downwards, and half as long as the thorax.

Dimensions.—Cephalis 0.025 long, 0.04 broad; thorax 0.09 long, 0.08 broad.

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

3. Sethophæna enneaptera, n. sp.

Shell rough, with sharp collar stricture. Length of the two joints = 1 : 6, breadth = 1 : 3. Cephalis subspherical, with a stout conical horn of twice the length. Thorax inversely ovate, with pointed, conical, basal part, and irregular, roundish pores. From its middle part arise, by a broad triangular base, nine compressed, divergent wings, which are a little curved, slender, and about as long as the thorax.

Dimensions.—Cephalis 0.025 long, 0.03 broad; thorax 0.17 long, 0.1 broad.

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

4. Sethophæna polyptera, n. sp.

Shell thorny, with slight collar stricture. Length of the two joints = 1 : 10, breadth = 3 : 8. Cephalis flat, cap-shaped, without horn. Thorax pear-shaped, with hemispherical base and regular, circular pores. From its lower half (beyond the equator) arises a corona of numerous short conical wings (eighteen to twenty-four), which are a little curved, and divergent downwards, scarcely one-third as long as the thorax.

Dimensions.—Cephalis 0.015 long, 0.04 broad; thorax 0.15 long, 0.12 broad.

Habitat.—North Pacific, Station 253, depth 3125 fathoms.

Genus 571. Clistophæna,^[188] Haeckel, 1881, Prodromus, p. 433.

Definition.—Sethophænida (vel Dicyrtida multiradiata clausa) with terminal apophyses. Cephalis with a horn.

The genus Clistophæna agrees with the preceding Sethophæna in the mouth of the thorax being closed by a lattice-plate. But the appendages of the thorax are terminal feet, not lateral wings; their number is commonly six or nine, rarely more. Clistophæna may be derived either from Tetrahedrina by interpolation of secondary feet between the three primary, or from Sethamphora by development of a basal lattice-plate closing the mouth.

1. Clistophæna rüstiana, n. sp. (Pl. 57, fig. 6).

Shell rough, with distinct collar stricture. Length of the two joints = 3 : 10, breadth = 4 : 11. Cephalis hemispherical, with small, circular pores and a stout oblique horn three times the length, which is three-sided prismatic, and at the top denticulate. Thorax subconical, inflate, with regular, circular, quincuncial pores, increasing in size towards the base. Margin of the flat base, with six divergent, stout feet of the same prismatic form as the cephalic horn, with denticulate distal ends, about as long as the thorax. This elegant species is dedicated to Dr. Rüst of Freiburg, the discoverer of numerous fossil Radiolaria in the Liassic and Jurassic formations.

Dimensions.—Cephalis 0.03 long, 0.04 broad; thorax 0.1 long, 0.11 broad.

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

2. Clistophæna hexolena, n. sp.

Shell smooth, with slight collar stricture. Length of the two joints = 1 : 4, breadth = 1 : 5. Cephalis subspherical, small, with a large, vertical, cylindrical horn, about as long as the shell, and small, circular pores. Thorax nearly three-sided pyramidal or tetrahedral, with three rounded edges and sub-regular, circular pores. Margin of the flat base with six conical, divergent, straight feet, somewhat shorter than the thorax. (Three on the corners, one on the middle of each side of the triangular base.)

Dimensions.—Cephalis 0.03 diameter, thorax 0.12 long, 0.14 broad.

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

3. Clistophæna pyramidalis, n. sp.

Shell smooth, with slight collar stricture. Length of the two joints = 2 : 8, breadth = 3 : 10. Cephalis hemispherical, with a stout pyramidal horn of twice the length. Thorax six-sided pyramidal, with regular, circular pores of equal size, and six prominent, straight edges, which are prolonged into six divergent, pyramidal feet of half the length.

Dimensions.—Cephalis 0.02 long, 0.03 broad; thorax 0.08 long, 0.1 broad.

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

4. Clistophæna armata, n. sp. (Pl. 57, fig. 7).

Shell spiny, with deep collar stricture. Length of the two joints = 4 : 18, breadth = 5 : 15. Cephalis subspherical, with small, circular, hexagonally-framed pores, and a stout, three-sided prismatic, cuspidate horn of the same length. Thorax pear-shaped, with regular, circular pores and three pairs of stout pyramidal wings, placed in the three primary meridional planes of the collar beams; three of them lie in the upper, and three in the lower third of the thorax. Margin of the flat base with nine cylindrical, somewhat club-shaped, divergent feet.

Dimensions.—Cephalis 0.04 long, 0.05 broad; thorax 0.18 long, 0.15 broad.

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

5. Clistophæna enneolena, n. sp.

Shell spiny, with sharp collar stricture. Length of the two joints = 4 : 20, breadth 5 : 16. Cephalis hemispherical, hyaline, with a stout conical horn of the same length and some small accessory horns. Thorax ovate, spiny, with subregular, circular pores. Margin of the vaulted base with nine divergent, conical feet, half as long as the thorax.

Dimensions.—Cephalis 0.04 long, 0.05 broad; thorax 0.2 long, 0.16 broad.

Habitat.—South Pacific, Station 296, depth 1825 fathoms.

6. Clistophæna polyolena, n. sp.

Shell smooth, conical, with obliterated collar stricture. Length of the two joints = 1 : 5, breadth = 2 : 5. Cephalis hemispherical, with small, circular pores and two divergent conical horns (a major occipital and a smaller frontal horn). Thorax obtusely conical, with regular, hexagonal pores at the mantle, and circular pores in the basal plate, the margin of which bears eighteen vertical, parallel, conical feet, as long as the cephalis.

Dimensions.—Cephalis 0.015 long, 0.025 broad; thorax 0.08 long, 0.08 broad.

Habitat.—Central Pacific, Stations 271 to 274, depth 2350 to 2750 fathoms.

Family LXIV.—Sethocyrtida, n. fam.

Definition.—Dicyrtida eradiata. (Cyrtoidea with a two-jointed shell, divided by a transverse constriction into cephalis and thorax, without radial apophyses).

The family Sethocyrtida, composed of the Sethocorida and Sethocapsida of my Prodromus, comprises those Cyrtoidea in which the shell is two-jointed and bears no radial apophyses. The two subfamilies differ in the shape of the mouth, which in the Sethocorida is a simple wide opening, and in the Sethocapsida is closed by a lattice-plate. The former are here divided into eight, the latter into three genera.

Numerous living and fossil forms of Sethocyrtida were previously described by Ehrenberg, partly in his genera Dictyocephalus and Lophophæna, partly (intermingled with three-jointed and many-jointed forms) in the genera Eucyrtidium and Lithocampe. A larger number of new forms has been found in the Radiolarian ooze collected by the Challenger, and others fossil in Barbados. Many of these Sethocyrtida are common and widely distributed. When a new third joint is formed on their basal mouth, they pass over into Theocyrtida.

The cephalis is usually subspherical or hemispherical, and much smaller than the thorax, the form of which exhibits all possible intermediate stages between flat, discoidal, conical, cylindrical, and ovate forms. The wide open mouth becomes more and more constricted, and finally closed in the Sethocapsida. The majority of the Sethocyrtida may have been derived either from the Tripocyrtida, or from the Anthocyrtida by reduction and loss of the radial apophyses.

Synopsis of the Genera of Sethocyrtida.

Subfamily 1. Sethocorida, Haeckel, Prodromus, p. 430.

Definition.—Sethocyrtida with the basal mouth of the shell open (vel Dicyrtida eradiata aperta).