Legion III. NASSELLARIA, (continued 9)

12. Lychnocanium hirundo, Ehrenberg.

Lychnocanium hirundo, Ehrenberg, 1875, Abhandl. d. k. Akad. d. Wiss. Berlin, p. 80, Taf. vii. fig. 8.

Lithornithium hirundo, Ehrenberg, 1854, Mikrogeol., Taf. xix. fig. 53.

Lithocampe hirundo, Ehrenberg, 1844, Monatsber. d. k. preuss. Akad. d. Wiss. Berlin, p. 65.

Shell conical, tuberculate, with slight collar stricture. Length of the two joints = 1 : 3, breadth = 1 : 4. Cephalis hemispherical, with a conical horn of half the length. Thorax campanulate, twice as broad as the flat mouth, with longitudinal, divergent ribs, alternating with rows of small circular pores. Three feet divergent, striated, gradually lessening from a broad base, twice as long as the thorax, curved like a crescent, with convexity outwards.

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

Habitat.—Fossil in Tertiary rocks of Barbados and the Mediterranean (Sicily, Greece).

13. Lychnocanium fenestratum, n. sp. (Pl. 61, fig. 10).

Shell pear-shaped, rough, with slight collar stricture. Length of the two joints = 1 : 4, breadth = 1 : 3. Cephalis subglobular, with a very large prismatic horn, which is about as long as the shell, with three denticulate, prominent, wing-like crests, which are pierced by a series of pores. Thorax ovate, three times as broad as the constricted, prominent mouth, with subregular, circular pores. Three feet arising somewhat above the mouth, prismatic, with denticulate edges, about as long as the thorax, divergent, curved, with convexity outwards.

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

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

14. Lychnocanium sigmopodium, n. sp. (Pl. 61, fig. 15).

? Lychnocanium tetrapodium, Ehrenberg, 1875, Abhandl. d. k. Akad. d. Wiss. Berlin, p. 80, Taf. vii. fig. 3.

Shell campanulate, rough with distinct collar stricture. Length of the two joints = 1 : 4, breadth = 1 : 3. Cephalis subspherical, with a slender pyramidal horn twice the length. Thorax inflated, conical, with regular circular pores and a wide open mouth of nearly the same breadth. Three feet widely divergent, twice as long as the thorax, angular, S-shaped, or curved with convexity inwards. (Lychnocanium tetrapodium of Ehrenberg is perhaps a variety of this species?).

Dimensions.—Cephalis 0.02 long, 0.03 broad; thorax 0.08 long, 0.09 broad.

Habitat.—Cosmopolitan; Mediterranean, Atlantic, Pacific, many stations at various depths; also fossil in Barbados and Sicily.

15. Lychnocanium trichopus, Ehrenberg.

Lychnocanium trichopus, Ehrenberg, 1875, Abhandl. d. k. Akad. d. Wiss. Berlin, p. 80, Taf. vii. fig. 5.

Shell conical, smooth, with deep collar stricture. Length of the two joints = 1 : 3, breadth = 1 : 3. Cephalis subspherical, with a rudimentary conical horn of half the length. Thorax campanulate, with regular, circular pores and wide open mouth of nearly the same breadth. Three feet divergent, very slender, four to five times as long as the thorax, not broader than one pore, S-shaped, or curved with convexity inwards in the distal half.

Dimensions.—Cephalis 0.02 long, 0.03 broad; thorax 0.07 long, 0.09 broad.

Habitat.—Fossil in Barbados.

Subgenus 3. Lychnocanoma, Haeckel.

Definition.—Feet parallel, vertical, straight, or little curved; divergent in the basal half, often convergent in the distal half; their terminal distance about equal to the basal distance.

16. Lychnocanium tripodium, Ehrenberg.

Lychnocanium tripodium, Ehrenberg, 1875, Abhandl. d. k. Akad. d. Wiss. Berlin, p. 80, Taf. vii. fig. 2.

Shell ovate, smooth, with distinct collar stricture. Length of the two joints = 1 : 4, breadth = 1 : 4. Cephalis subglobular, with a slender conical horn twice the length. Thorax inflated, twice as broad as the constricted mouth, with small, regular, circular pores. Three feet slender, prismatic, twice to three times as long as the thorax, nearly straight and parallel, vertical.

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

Habitat.—Central Pacific, Stations 265 to 268, depth 2700 to 2900 fathoms; also fossil in Barbados.

17. Lychnocanium cypselus, Ehrenberg.

Lychnocanium cypselus, Ehrenberg, 1875, Abhandl. d. k. Akad. d. Wiss. Berlin, p. 78, Taf. vii. fig. 10.

Shell slender, ovate, with slight collar stricture. Length of the two joints = 1 : 4, breadth = 1 : 3. Cephalis subspherical, with a conical horn of the same length. Thorax ovate, truncate, three times as broad as the narrow, constricted mouth, with small, regular, circular pores. Three feet slender, somewhat shorter than the thorax, little curved, with convexity outwards, nearly parallel, vertical. (In the specimen figured by Ehrenberg, the third foot was broken off.)

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

Habitat.—Fossil in Barbados.

18. Lychnocanium ovatum, n. sp.

Shell ovate, rough, without external collar stricture. Length of the two joints = 1 : 6, breadth = 1 : 5. Cephalis conical, with a stout conical horn of the same length. Thorax ovate, four times as broad as the narrow constricted mouth, with small, regular, circular pores, separated by hexagonal frames of twice the breadth. Three feet cylindrical, half as long as the thorax, and three times as long as broad, straight, parallel, vertical.

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

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

19. Lychnocanium crassipes, Ehrenberg.

Lychnocanium crassipes, Ehrenberg, 1875, Abhandl. d. k. Akad. d. Wiss. Berlin, p. 78, Taf. vii. fig. 7.

Shell campanulate, rough, with deep collar stricture. Length of the two joints = 1 : 3, breadth = 1 : 4. Cephalis subspherical, with a thin conical horn of the same length. Thorax semi-ovate, three times as broad as the narrow constricted mouth, with fifteen to twenty divergent, denticulate ribs, alternating with the same number of rows of small, regular, circular pores. Three feet very stout, as long as the thorax, cylindrical, nearly straight and parallel, vertical, at the distal end clavate, spinulate or a little forked.

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

Habitat.—Fossil in Barbados.

20. Lychnocanium clavigerum, n. sp. (Pl. 61, fig. 4).

Shell campanulate, sulcate, with sharp collar stricture. Length of the two joints = 1 : 4, breadth = 1 : 5. Cephalis subglobular, with a spindle-shaped papillate horn twice the length. Thorax nearly spherical, truncate at both poles, three times as broad as the narrow, constricted, somewhat tubular mouth, with fifteen to twenty elevated meridional ribs, alternating with the same number of rows of circular pores. Three feet slender, cylindrical, twice as long as the thorax, in the basal half divergent, in the distal half convergent, club-shaped, with a thickened papillate end.

Dimensions.—Cephalis 0.02 long, 0.025 broad; thorax 0.08 long, 0.01 broad.

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

21. Lychnocanium pudicum, n. sp. (Pl. 61, fig. 2).

Shell campanulate, with deep collar stricture. Length of the two joints = 1 : 3, breadth = 1 : 3. Cephalis hemispherical, hyaline (without pores), with a short and thick club-shaped, spinulate horn of the same length. Thorax subglobular, truncate at both poles, twice as broad as the constricted mouth, with small, irregular, roundish pores. Three feet somewhat shorter than the thorax, curved like a crescent, with convexity outwards; their distal ends club-shaped, spinulate, convergent towards the central axis.

Dimensions.—Cephalis 0.02 long, 0.025 broad; thorax 0.06 long, 0.07 broad.

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

Genus 549. Lychnodictyum,^[166] Haeckel, 1881, Prodromus, p. 432.

Definition.—Sethopilida (vel Dicyrtida triradiata aperta), with three latticed terminal feet on the peristome, without thoracic ribs. Cephalis originally with a horn (sometimes lost).

The genus Lychnodictyum differs from the preceding Lychnocanium only in the fenestration of the three terminal feet, and bears therefore to it the same relation that the ancestral Tripocyrtis does to Dictyophimus.

1. Lychnodictyum challengeri, Haeckel.

Dictyopodium challengeri, Wyville Thomson, 1877, Atlantic, vol. i. p. 234, fig. 52.

Dictyophimus (vel Tripocyrtis) challengeri, Haeckel, 1878, Protistenreich, p. 47, fig. 35.

Shell campanulate, smooth, with sharp collar stricture. Length of the two joints = 1 : 3, breadth = 1 : 4. Cephalis subspherical, with a large, oblique, pyramidal horn thrice the length. Thorax with three inflated bosoms between the three decurrent ribs, which are prolonged into three vertical, parallel, pyramidal, in the upper half fenestrated feet, as long as the thorax. Pores regular, circular. Mouth constricted, flat, half as broad as the thorax.

Dimensions.—Cephalis 0.03 diameter; thorax 0.08 long, 0.12 broad.

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

2. Lychnodictyum wyvillei, n. sp.

Shell pyramidal, smooth, with obliterated collar stricture. Length of the two joints = 1 : 3, breadth = 1 : 5. Cephalis subspherical, with a large, straight, pyramidal horn of twice the length. Thorax nearly tetrahedral, inflated, with three rounded, decurrent ribs, which are prolonged into three widely divergent, angular, curved feet, about as long as the shell, with pyramidal fenestrated base. Pores regular, circular. Mouth constricted, flat, half as broad as the thorax.

Dimensions.—Cephalis 0.025 diameter; thorax 0.08 long, 0.12 broad.

Habitat.—Central Pacific, Stations 266 to 274, depth 2350 to 2925 fathoms.

3. Lychnodictyum scaphopodium, n. sp. (Pl. 56, fig. 4).

Cephalis hemispherical, large, without horn, with irregular, small, roundish pores. Thorax a little larger, campanulate, with three broad, shovel-shaped, fenestrated, vertical feet, and larger, irregular pores. In the figured specimen the third (posterior) foot was broken off. In another specimen the three feet were somewhat longer and not so broad.

Dimensions.—Cephalis 0.03 long, 0.05 broad; thorax 0.05 long, 0.06 broad.

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

4. Lychnodictyum sethopodium, n. sp.

Cephalis hemispherical, large, with a rudimentary conical horn, and very scarce small pores. Thorax twice as broad and long as the cephalis, campanulate, with irregular, roundish pores, and three slender, pyramidal, divergent feet twice the length, which in the upper half are fenestrated, in the lower half solid.

Dimensions.—Cephalis 0.025 long, 0.045 broad; thorax 0.05 long, 0.09 broad.

Habitat.—South Atlantic, Station 330, surface.

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

Definition.—Tripocyrtida with the basal mouth of the shell fenestrated (vel Dicyrtida triradiata clausa).

Genus 550. Sethopera,^[167] Haeckel, 1881, Prodromus, p. 433.

Definition.—Sethoperida (vel Dicyrtida triradiata clausa), with three divergent ribs enclosed in the latticed wall of the thorax. Cephalis with a horn.

The genus Sethopera is probably the oldest form of the Sethoperida, and may therefore be regarded as the common ancestral form of this subfamily. The thorax exhibits three radial ribs, which are completely enclosed in its wall. Sethopera may be derived either from Dictyophimus or from another of the Sethopilida (Lamprodiscus, Clathrocanium) by development of a basal lattice-plate closing the mouth. There are often wide holes or open spaces between the three radial ribs.

1. Sethopera tricostata, n. sp. (Pl. 97, fig. 11).

Cephalis subspherical, spinulate, with a pyramidal horn of the same length. Length of the two joints = 5 : 8, breadth = 5 : 8. Thorax also nearly spherical; in the upper half with three stout, prismatic, convex, divergent ribs, and three large ovate holes between them; in the lower half with numerous small and irregular pores, spinulate.

Dimensions.—Cephalis 0.05 diameter; thorax 0.08 diameter.

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

2. Sethopera oceania, Haeckel.

Lithopera oceania, Ehrenberg, 1872, Abhandl. d. k. Akad. d. Wiss. Berlin, p. 297, Taf. iv. fig. 21.

Cephalis hemispherical, with a small bristle-shaped horn of half the length (broken off in Ehrenberg's figure). Length of the two joints = 3 : 4, breadth = 3 : 4. Thorax nearly spherical; in the upper half with three divergent ribs, separated by some larger, irregular pores; in the lower half with numerous small, irregular, roundish pores.

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

Habitat.—North Atlantic, Station 354, surface; Canary Islands and Azores.

3. Sethopera pyrum, Haeckel.

? Lithopera pyrum, Ehrenberg, 1872, Abhandl. d. k. Akad. d. Wiss. Berlin, p. 297.

Cephalis hemispherical, with a small conical horn of half the length. Length of the two joints = 3 : 10, breadth = 3 : 7. Thorax pear-shaped, with rather large, regular, quincuncial pores; its upper half with three divergent ribs in the wall, half as broad as the subspherical lower half. (The three ribs probably were overlooked by Ehrenberg.)

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

Habitat.—North Pacific, Station 256, surface; Californian Sea, 2600 fathoms, Ehrenberg.

4. Sethopera lagena, Haeckel.

Lithopera lagena, Ehrenberg, 1875, Abhandl. d. k. Akad. d. Wiss. Berlin, p. 78, Taf. iii. fig. 4.

Cephalis pear-shaped, with a small conical horn of half the length. Length of the two joints = 3 : 8, breadth = 3 : 6. Thorax smooth, pear-shaped, with irregular roundish pores; in the wall of its upper third three divergent thin ribs (sometimes wanting); the lower half inflated. (Compare Sethocapsa lagena.)

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

Habitat.—Fossil in Barbados.

Genus 551. Lithopera,^[168] Ehrenberg, 1847, Monatsber. d. k. preuss. Akad. d. Wiss. Berlin, p. 54.

Definition.—Sethoperida (vel Dicyrtida triradiata clausa), with three divergent ribs enclosed in the cavity of the thorax. Cephalis with a horn.

The genus Lithopera is, like the preceding Sethopera, one of the most simple and oldest forms of the Sethoperida, and exhibits three divergent thoracic ribs, which are prolonged neither into lateral wings nor into basal feet. But whilst in Sethopera the three ribs are enclosed in the lattice-work of the shell-wall, in Lithopera they lie freely in its cavity, and are overgrown by the enveloping shell-wall, being inserted on its inner face with their distal ends. Lithopera may be derived directly from Lithomelissa, by development of lattice-work closing the shell-mouth. Therefore the lower part of the cephalis is hidden in the uppermost part of the thorax; only its upper part is free.

1. Lithopera bacca, Ehrenberg.

Lithopera bacca, Ehrenberg, 1872, Abhandl. d. k. Akad. d. Wiss. Berlin, p. 297, Taf. viii. fig. 1.

Cephalis spherical, with small, irregular pores and a bristle-shaped spine of half the length; its lower half hidden in the thorax. Length of the two joints = 1 : 6, breadth = 1 : 5. Thorax ellipsoidal, smooth, with regular, hexagonal, small pores, and very thin, thread-like bars. From the deep collar stricture there arise three internal, divergent bars, which are inserted at the uppermost third of the thorax.

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

Habitat.—Tropical Pacific, Stations 200, 224, 266, 271, &c., surface.

2. Lithopera bursella, Ehrenberg.

Lithopera bursella, Ehrenberg, 1872, Abhandl. d. k. Akad. d. Wiss. Berlin, p. 297, Taf. x. fig. 4.

Shell of about the same form and structure as in the nearly allied preceding species, but smaller, of more slender form, with smaller pores and thinner bars. Length of the two joints = 1 : 5, breadth = 1 : 3. In the specimen observed by me the three internal, divergent bars of the ellipsoidal thorax (not seen by Ehrenberg) were as distinct as in the similar preceding and following species.

Dimensions.—Cephalis 0.02 diameter; thorax 0.1 long, 0.06 broad.

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

3. Lithopera ananassa, n. sp. (Pl. 57, fig. 3).

Shell of about the same form and structure as in the two preceding species, but larger and more robust, and differing in the spiny surface. Length of the two joints = 1 : 5, breadth = 1 : 4. Here also the lower half of the spherical cephalis is submerged in the ellipsoidal thorax, and from the collar stricture arise three strong, internal, divergent beams. The bars of the hexagonal pores are much thicker than in the two preceding species.

Dimensions.—Cephalis 0.03 diameter; thorax 0.16 long, 0.12 broad.

Habitat.—Tropical Atlantic, Stations 347 to 352, surface.

4. Lithopera globosa, n. sp.

Cephalis spherical, very small, with two divergent conical horns of half the length; its lower half hidden in the thorax. Length of the two joints = 1 : 5, breadth = 1 : 5. Thorax spherical, with regular, circular, hexagonally-framed pores. From the collar stricture arise three radial internal beams, horizontally diverging, and inserted at the inside of the thorax.

Dimensions.—Cephalis 0.03 diameter; thorax 0.15 diameter.

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

5. Lithopera gutta, Ehrenberg.

Lithopera gutta, Ehrenberg, 1872, Abhandl. d. k. Akad. d. Wiss. Berlin, p. 297, Taf. viii. fig. 2.

Shell pear-shaped, with sharp collar stricture. Length of the two joints = 1 : 4, breadth = 1 : 3. Cephalis spherical, with a conical horn of the same length; its lower half hidden in the uppermost part of the ovate thorax, and connected with its wall by three internal, cortinar beams. Pores of the thorax very irregular in form and size, partly lobed.

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

Habitat.—Western Tropical Pacific, Station 225, depth 4475 fathoms; Philippine Sea (depth 3300 fathoms), Ehrenberg.

Genus 552. Micromelissa,^[169] Haeckel, 1881, Prodromus, p. 433.

Definition.—Sethoperida (vel Dicyrtida triradiata clausa), with three divergent, solid, lateral wings. Cephalis with a horn.

The genus Micromelissa differs from the two preceding genera in the free prominence of the three cortinar ribs, forming three solid lateral wings. Beyond these the thorax walls are convergent, and the basal mouth closed by a lattice-plate. Therefore Micromelissa may have arisen from Lithomelissa simply by development of this basal mouth-plate.

1. Micromelissa bombus, n. sp. (Pl. 57, fig. 14).

Shell smooth, with sharp collar stricture. Length of the two joints = 1 : 4, breadth = 1 : 5. Cephalis spherical, with an oblique conical horn of the same length. Thorax subspherical, in the upper half with three conical, downwardly diverging wings, about as long as its radius. Pores very small and scarce.

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

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

2. Micromelissa vespa, n. sp.

Shell smooth, with deep collar stricture. Length of the two joints = 2 : 5, breadth = 2 : 3. Cephalis spherical, with an oblique pyramidal horn twice the length. Thorax inversely ovate, in the upper half with three pyramidal wings, which are equal to its breadth, little curved and diverging downwards. Pores very small and scarce.

Dimensions.—Cephalis 0.04 diameter; thorax 0.1 long, 0.06 broad.

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

3. Micromelissa apis, n. sp.

Shell rough, with deep collar stricture. Length of the two joints = 2 : 3, breadth = 2 : 4. Cephalis subspherical, with a straight conical horn of half the length, and subregular, circular, double-contoured pores, of the same breadth as the bars. Thorax little larger, subspherical, with irregular, roundish pores, twice to four times as broad as the bars. From its lower half arise three short conical wings, curved downwards, and half as long as the cephalis.

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

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

4. Micromelissa microptera, Haeckel.

Lithomelissa microptera, Ehrenberg, 1854, Mikrogeol., Taf. xxxvi. fig. 2; Abhandl. d. k. Akad. d. Wiss. Berlin, 1875, p. 78, Taf. iii. fig. 13.

Lithomelissa microptera, Bütschli, 1882, Zeitschr. f. wiss. Zool., vol. xxxvi. p. 539, Taf. xxxiii. fig. 26.

Shell smooth, with distinct collar stricture. Length of the two joints = 4 : 6, breadth = 3 : 5. Cephalis ovate, with a straight sword-shaped horn of the same length and very small pores, some larger ones above the stricture. Thorax little larger, ovate, nearly hyaline, with very few and small scattered pores. From its uppermost part arise three short conical wings, scarcely half as long as the cephalic horn, little curved and divergent downwards.

Dimensions.—Cephalis 0.04 long, 0.03 broad; thorax 0.06 long, 0.05 broad.

Habitat.—Fossil in Barbados.

5. Micromelissa ventricosa, Haeckel.

Lithomelissa ventricosa, Ehrenberg, 1875, Abhandl. d. k. Akad. d. Wiss. Berlin, p. 78, Taf. iii. fig. 11.

Shell rough, with slight collar stricture. Length of the two joints = 1 : 7, breadth = 1 : 5. Cephalis small, hemispherical, with a small conical horn of half the length. Thorax ovate, very large, papillate, with irregular, roundish pores. From its basal part arise three short and stout conical wings at great distances, shorter than the cephalis. (A transition-form to Sethocapsa.)

Dimensions.—Cephalis 0.02 long, 0.022 broad; thorax 0.14 long, 0.11 broad.

Habitat.—Fossil in Barbados.

Genus 553. Peromelissa,^[170] Haeckel, 1881, Prodromus, p. 433.

Definition.—Sethoperida (vel Dicyrtida triradiata clausa) with three divergent solid lateral wings. Cephalis without horn.

The genus Peromelissa differs from the preceding ancestral form, Micromelissa, only in the absence of the cephalic horn, which is lost by reduction.

1. Peromelissa phalacra, n. sp. (Pl. 57, fig. 11).

Shell smooth, with two joints of nearly equal size and similar ovate form. Cephalis in the upper half hyaline, without pores; in the lower half with four remote, transverse rows of irregular, roundish pores, decreasing in size towards the hemispherical summit. Thorax with twelve transverse rows of pores, the upper six rows three to four times as large as the lower six rows. From its upper half diverge almost horizontally three angular club-shaped wings, half as long as the shell.

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

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

2. Peromelissa psilocrana, n. sp.

Shell smooth, very similar to the preceding species in size and form, but differing from it in the disposition of the irregular, roundish pores, which are irregularly scattered, and in the form of the three wings, which are slender, pyramidal, diverging downwards, and about as long as the entire shell.

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

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

3. Peromelissa capito, Haeckel.

Lithomelissa capito, Ehrenberg, 1875, Abhandl. d. k. Akad. d. Wiss. Berlin, p. 78, Taf. iii. fig. 14.

Shell rough, with two joints of nearly equal size and similar ovate form. Pores irregular, roundish, everywhere scattered. From the upper half of the thorax arise three short conical wings, which are little curved and diverge downwards (scarcely half as long as the breadth of the shell).

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

Habitat.—Fossil in Barbados.

4. Peromelissa calva, n. sp. (Pl. 57, fig. 12).

Shell rough, with two ovate joints of somewhat different sizes. Pores irregular, roundish, everywhere scattered. Thorax little larger than the cephalis; from its upper half arise three short conical wings, diverging downwardly or nearly horizontally.

Dimensions.—Cephalis 0.06 long, 0.04 broad; thorax 0.07 long, 0.05 broad.

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

Genus 554. Sethomelissa,^[171] Haeckel, 1881, Prodromus, p. 431.

Definition.—Sethoperida (vel Dicyrtida triradiata clausa) with three divergent latticed lateral wings. Cephalis with a horn (or a bunch of horns).

The genus Sethomelissa differs from the nearly allied Micromelissa in the fenestration of the three lateral wings, and may be derived either from this genus by development of lattice-work connecting the three wings with the shell, or perhaps from Clathrocanium by closing the mouth.

1. Sethomelissa hymenoptera, n. sp.

Cephalis subspherical, thorny, with a bunch of three divergent, larger apical spines. Thorax pear-shaped, with three broad, triangular, latticed wings, the superior edge of which is a horizontal, straight, and stout spine, nearly as long as the thorax. Pores irregular, roundish.

Dimensions.—Cephalis 0.03 diameter; thorax 0.11 long, 0.08 broad.

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

Genus 555. Tetrahedrina,^[172] Haeckel, 1881, Prodromus, p. 433.

Definition.—Sethoperida (vel Dicyrtida triradiata clausa) with a three-sided pyramidal thorax, the three edges of which are prolonged into three divergent, solid, terminal feet. Cephalis with a horn.

The genus Tetrahedrina, and the two following nearly allied genera, are distinguished by the possession of three free, divergent, terminal feet, projecting over the latticed mouth of the thorax. Tetrahedrina may be derived directly from Dictyophimus, by development of a horizontal latticed mouth-plate from the middle part of the feet, the lower part of which remains free. This genus, not noticed by Ehrenberg, is similar to his Lithochytris, and common in the Barbados deposits.

1. Tetrahedrina pyramidalis, n. sp.

Shell three-sided pyramidal, smooth, with slight collar stricture. Length of the two joints = 1 : 4, breadth = 1 : 4. Cephalis hemispherical, with small, sparsely disposed pores, and a pyramidal horn of the same length. Thorax with subregular, circular pores and three sharp edges, prolonged into three divergent pyramidal feet of the same length.

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

Habitat.—Fossil in Barbados.

2. Tetrahedrina pyriformis, n. sp.

Shell pear-shaped, rough, with distinct collar stricture. Length of the two joints = 2 : 6, breadth = 2 : 5. Cephalis subspherical, with a conical horn of the same length. Thorax with subregular, circular pores, ovate, at the broad base with three pyramidal, widely divergent feet of the same length. (Similar to Lychnocanium tribulus, Ehrenberg, 1875, loc. cit., pl. vii. fig. 1, but with the mouth closed by a lattice-plate.)

Dimensions.—Cephalis 0.04 diameter; thorax 0.12 long, 0.1 broad,

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

3. Tetrahedrina quadricornis, Haeckel.

Lithochytris triangula, Bury, 1862, Polycystins of Barbados, pl. xix. figs. 4, 5, 6.

Shell pear-shaped, papillate, with slight collar stricture. Length of the two joints = 1 : 5, breadth = 1 : 5. Cephalis subspherical, with a stout conical horn twice the length. Thorax with irregular, roundish, lobulated pores, with three conical, stout, divergent feet at the base, of the same size and form as the cephalic horn.

Dimensions.—Cephalis 0.02 diameter; thorax 0.1 long, 0.1 broad.

Habitat.—Fossil in Barbados.

Genus 556. Sethochytris,^[173] Haeckel, 1881, Prodromus, p. 433.

Definition.—Sethoperida (vel Dicyrtida triradiata clausa) with three terminal latticed feet or hollow, fenestrated, divergent, basal apophyses of the thorax. Cephalis with a horn.

The genus Sethochytris differs from the preceding Tetrahedrina in the fenestration of the three basal feet, which form direct protrusions or evaginations of the three basal corners of the pyramidal shell. It may be derived from Sethopera by centrifugal growth of the basal corners.

1. Sethochytris triconiscus, n. sp. (Pl. 57, fig. 13).

Shell rough, with deep collar stricture. Length of the two joints = 1 : 8, breadth = 1 : 3. Cephalis spherical, with an oblique pyramidal horn of the same length. Thorax campanulate, conical; its three basal corners prolonged into three divergent, slender, hollow, fenestrated cones, twice as long as the thorax, and ending in a stout pyramidal spine.

Dimensions.—Cephalis 0.04 diameter, thorax 0.12 diameter, length of the feet 0.2.

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

2. Sethochytris barbadensis, Haeckel.

Lithochytris barbadensis, Ehrenberg, 1875, Abhandl. d. k. Akad. d. Wiss. Berlin, p. 160, Taf. v. fig. 2.

Shell smooth, with slight collar stricture. Length of the two joints = 1 : 6, breadth = 1 : 4. Cephalis ovate, with a conical horn of half the length. Thorax conical; its base prolonged into three divergent, hollow, fenestrated cones, half as long as the thorax. Pores small, subregular, circular.

Dimensions.—Cephalis 0.025 diameter, thorax 0.1 diameter, length of the feet 0.05.

Habitat.—Fossil in Barbados.

3. Sethochytris pyramis, n. sp.

Shell smooth, with slight collar stricture. Length of the two joints = 1 : 8, breadth = 1 : 5. Cephalis ovate, with a conical horn of half the length. Thorax pyramidal, with three sharp edges; its base prolonged into three pyramidal, divergent, hollow, fenestrated feet, nearly as long as the thorax. Pores regular, circular, double-contoured.

Dimensions.—Cephalis 0.04 diameter; thorax 0.2 diameter, length of the feet 0.15.

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

4. Sethochytris triangula, Haeckel.

Lithochytris triangula, Bury, 1862, Polycystins of Barbados, pl. xix. fig. 7.

Shell rough, with obliterated collar stricture (but distinct internal collar septum). Length of the two joints = 1 : 6, breadth = 1 : 3. Cephalis subspherical, with a stout conical horn of the same length. Thorax pear-shaped, inflated; its base prolonged into three divergent, hollow, fenestrated cones, about as long as the thorax. Pores regular, circular.

Dimensions.—Cephalis 0.03 diameter; thorax 0.09 diameter, length of the feet 0.1.

Habitat.—Fossil in Barbados.

Genus 557. Clathrolychnus,^[174] Haeckel, 1881, Prodromus, p. 431.

Definition.—Sethoperida (vel Dicyrtida triradiata clausa), with three vertical, lateral latticed wings stretched between the apical horn and the three terminal feet. The external lattice-work connecting the wings and closing the mouth forms an arachnoidal mantle around the shell.

The genus Clathrolychnus may be derived directly from Clathrocorys, by development of an external arachnoidal mantle connecting the three wings and the three feet, and enveloping the whole shell, closing at the same time the basal mouth of the thorax by a fenestrated plate.

1. Clathrolychnus araneosus, n. sp. (Pl. 64, fig. 5).

Cephalis subspherical, with irregular, polygonal pores and a large pyramidal horn of twice the length. Length of the two joints = 4 : 9, breadth = 5 : 12. Thorax with three large triangular holes (twice as broad as the cephalis) between the three pyramidal, divergent feet, which at the distal end are connected by a narrow band of network, composed of two or three rows of polygonal pores. The entire pyramidal shell is enveloped by a very delicate web of irregular, polygonal meshes, closing also the basal mouth. (In fig. 5 the greater part of the web is taken off to demonstrate the large holes of the thorax). Only two feet are visible.

Dimensions.—Cephalis 0.04 long, 0.05 broad; thorax 0.09 long, 0.12 broad.

Habitat.—Central Pacific, Station 274, surface.

2. Clathrolychnus periplectus, n. sp. (Pl. 64, fig. 6).

Cephalis subspherical, with subregular, circular pores and a pyramidal horn of the same length. Length of the two joints = 1 : 2, breadth = 1 : 3. Thorax with three large elliptical holes between the three pyramidal, divergent feet, which are connected at the distal end by a broad band of network, composed of five to ten rows of polygonal pores. The entire pyramidal shell is enveloped by a very delicate web, which on the sides is composed of subregular, square meshes, and on the closed mouth of polygonal meshes. (In fig. 6 only a part of the web is represented.)

Dimensions.—0.04 long, 0.05 broad; thorax 0.08 long, 0.14 broad.

Habitat..—Central Pacific, Station 271, surface.

Family LXIII. Anthocyrtida, n. fam.

Definition.—Dicyrtida multiradiata. (Cyrtoidea with a two-jointed shell, divided by a transverse constriction into cephalis and thorax, and bearing numerous—four to nine or more—radial apophyses.)

The family Anthocyrtida, composed of the Sethophormida and Sethophænida of my Prodromus, comprises those Cyrtoidea in which the shell is two-jointed and bears numerous radial apophyses. The two subfamilies differ in the shape of the mouth, which in the Sethophormida is a simple, wide opening; in the Sethophænida closed by a lattice-plate.

Numerous fossil and living forms of Anthocyrtida were described formerly by Ehrenberg in his genera Carpocanium and Anthocyrtis. These, however, represent only a small part of the whole family, which exhibits a great variety in the composition of the lattice-work and in the number of radial beams. The number of species here described amounts to one hundred and forty, and these are disposed in fourteen genera (twelve Sethophormida and two Sethophænida).

The Sethophormida may be again divided into two different groups or tribes, the Sethamphorida and Carpocanida; in the former the thorax bears numerous radial ribs, enclosed in its wall; in the latter these ribs have disappeared, and only a corona of terminal feet is developed around the mouth. The shell of the former is usually pyramidal, with a widely open mouth; of the latter ovate, with a constricted mouth. The mouth of the thorax becomes perfectly closed in the Sethophænida.

The majority of the Anthocyrtida may be derived from the Polyspyrida (Petalospyris, &c.) by reduction of the cephalis and loss of the sagittal ring, as was suggested by Bütschli (1882, loc. cit.). But another part may also have arisen from the Tripocyrtida, by interpolation of secondary radial apophyses between the three primary perradial apophyses. The cephalis in this family is developed in all possible degrees, from one of a considerable size to one very much reduced. If it becomes perfectly lost, the Cyrtocalpida arise.

Synopsis of the Genera of Anthocyrtida.

I. Subfamily Sethophormida. Terminal mouth of the thorax a simple wide opening. Radial ribs smooth (rarely thorny) enclosed in the wall of the thorax (cephalis commonly small, without horns). Shell flat, campanulate or nearly discoidal (cephalis without horn), 558. Sethophormis.

Shell ovate, with constricted mouth (without horn), 559. Sethamphora.

Shell slender pyramidal, with straight ribs. Meshes of the network simple, 560. Sethopyramis.

Meshes fenestrated by secondary latticework, 561. Plectopyramis.

Meshes closed by spongy framework, 562. Spongopyramis.

Radial ribs thorny (rarely smooth) prolonged into free terminal feet (cephalis commonly large, with one or more horns). Shell not enveloped by arachnoidal network, 563. Acanthocorys.

Shell enveloped by arachnoidal network, 564. Arachnocorys.

No ribs in the thorax. Peristome with free terminal feet. Cephalis well-developed with an apical horn. Feet terminal, without separate peristome. Six feet, 565. Anthocyrtoma.

Nine feet, 566. Anthocyrtis.

Twelve or more feet, 567. Anthocyrtium.

Feet subterminal, outside the constricted peristome, 568. Anthocyrtidium.

Cephalis rudimentary, hidden in the upper part of the thorax, without horn, 569. Carpocanium.

II. Subfamily Sethophænida. Terminal mouth closed by a lattice-plate. Thorax with lateral apophyses (four to six or more wings), 570. Sethophæna.

Thorax with terminal apophyses (four to six or more feet), 571. Clistophæna.

I. Subfamily Sethophormida. Terminal mouth of the thorax a simple wide opening.

Radial ribs smooth (rarely thorny) enclosed in the wall of the thorax (cephalis commonly small, without horns).

Shell flat, campanulate or nearly discoidal (cephalis without horn),

558. Sethophormis.

Shell ovate, with constricted mouth (without horn),

559. Sethamphora.

Shell slender pyramidal, with straight ribs.

Meshes of the network simple,

560. Sethopyramis.

Meshes fenestrated by secondary latticework,

561. Plectopyramis.

Meshes closed by spongy framework,

562. Spongopyramis.

Radial ribs thorny (rarely smooth) prolonged into free terminal feet (cephalis commonly large, with one or more horns).

Shell not enveloped by arachnoidal network,

563. Acanthocorys.

Shell enveloped by arachnoidal network,

564. Arachnocorys.

No ribs in the thorax. Peristome with free terminal feet.

Cephalis well-developed with an apical horn.

Feet terminal, without separate peristome.

Six feet,

565. Anthocyrtoma.

Nine feet,

566. Anthocyrtis.

Twelve or more feet,

567. Anthocyrtium.

Feet subterminal, outside the constricted peristome,

568. Anthocyrtidium.

Cephalis rudimentary, hidden in the upper part of the thorax, without horn,

569. Carpocanium.

II. Subfamily Sethophænida. Terminal mouth closed by a lattice-plate.

Thorax with lateral apophyses (four to six or more wings),

570. Sethophæna.

Thorax with terminal apophyses (four to six or more feet),

571. Clistophæna.

Subfamily 1. Sethophormida, Haeckel, 1881, Prodromus, p. 432.

Definition.—Anthocyrtida with the basal mouth of the shell open (vel Dicyrtida multiradiata aperta).

Genus 558. Sethophormis, Haeckel,^[175] 1881, Prodromus, p. 432.

Definition.—Sethophormida (vel Dicyrtida multiradiata aperta) with numerous radial ribs in the wall of the flat and broad campanulate or nearly discoidal thorax. Cephalis also flat and broad, cap-shaped without horn.

The genus Sethophormis comprises a great number of widely distributed and large Dicyrtida, all agreeing in the flat cap-shaped or nearly discoidal form of the thorax, which has constantly a very delicate network, and is pierced by numerous radial beams. Four of these are commonly primary and direct prolongations of the four cortinar rods in the collar septum, whilst the others are secondary or interpolated ribs. Sethophormis may be derived either from the triradial Lamprodiscus by multiplication of the ribs (or interpolation of secondary ribs between the three primary), or from Halicalyptra by development of transverse rods connecting its terminal feet, and forming a ribbed thorax. Corresponding to the number of the ribs, we may distinguish as subgenera (separate genera in my Prodromus, 1881, p. 432) Tetraphormis with four, Pentaphormis with five, Hexaphormis with six, Octophormis with eight, Enneaphormis with nine, and Astrophormis with ten to twenty or more ribs. The cephalis bears no horn, and is usually large, flat, cap-shaped or hemispherical.

Subgenus 1. Tetraphormis, Haeckel, 1881, Prodromus, p. 432.

Definition.—Thorax with four radial ribs opposite in pairs in two meridional planes, perpendicular to one another. Collar septum with four large pores.

1. Sethophormis cruciata, n. sp.

Cephalis very large, hemispherical with irregular, delicate network of small square meshes. Thorax flatly campanulate, with delicate, regular network of small hexagonal meshes. All bars very thin, thread-like. Four stout radial thoracic ribs, crossed in pairs, lie in two meridional planes, perpendicular to one another. Very similar to Sethophormis aurelia (Pl. 55, figs. 3, 4), but not so flat, and with only four thoracic ribs. Peristome or margin of the thoracic mouth smooth, circular.

Dimensions.—Cephalis 0.04 long, 0.08 broad; thorax 0.12 long, 0.36 broad.

Habitat.—Central Pacific, Station 271, surface.

2. Sethophormis medusa, n. sp.

Cephalis very large, flat, cap-shaped, with irregular, delicate network of polygonal meshes. Thorax flat, campanulate, nearly hemispherical, with delicate, irregular network of small polygonal meshes. All bars very thin, thread-like. Four stout radial thoracic ribs, as in the preceding species. Peristome denticulate.

Dimensions.—Cephalis 0.03 long, 0.09 broad; thorax 0.15 long, 0.25 broad.

Habitat.—North Pacific, Station 244, surface.

Subgenus 2. Pentaphormis, Haeckel, 1881, Prodromus, p. 432.

Definition.—Thorax with five radial ribs, one of the three primary ribs (the odd occipital rib) being simple, the two others (the paired lateral ribs) forked.

3. Sethophormis pentalactis, n. sp. (Pl. 56, fig. 5).

Cephalis large, flat, hemispherical, with subregular, hexagonal pores. Thorax flat, campanulate, nearly hemispherical; also with subregular, hexagonal pores, and with five stout ribs. The three primary ribs of the thorax are complete, and reach the peristome; the two secondary ribs (as basal branches of the two lateral ribs) are incomplete and absent in the distal half of the thorax. Peristome denticulate, with an elegant marginal corona of small square pores and short conical spines.

Dimensions.—Cephalis 0.03 long, 0.06 broad; thorax 0.1 long, 0.2 broad.

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

4. Sethophormis asteriscus, n. sp.

Cephalis large, flat, cap-shaped, with irregular polygonal pores. Thorax flat, campanulate, with subregular, hexagonal pores, and five stout ribs. The marginal distance between the two anterior (lateral) ribs is twice as great as the distance between every two other ribs (the postero-lateral ribs being basal branches of the antero-lateral ribs). Peristome with a double corona of short, conical spines.

Dimensions.—Cephalis 0.02 long, 0.04 broad; thorax 0.06 long, 0.17 broad.

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

5. Sethophormis astrodiscus, n. sp.

Cephalis small, flatly vaulted, cap-shaped with irregular polygonal pores. Thorax very flatly vaulted, nearly discoidal, with subregular hexagonal pores, and five stout ribs. The marginal distance between all five ribs is nearly equal. Peristome denticulate with an elegant corona of small square pores and short conical thorns.

Dimensions.—Cephalis 0.015 long, 0.035 broad; thorax 0.05 long, 0.2 broad.

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

Subgenus 3. Hexaphormis, Haeckel, 1881, Prodromus, p. 432.

Definition.—Thorax with six radial ribs (three primary perradial and three secondary interradial beams).

6. Sethophormis hexalactis, n. sp. (Pl. 56, fig. 6).

Cephalis large, hemispherical, with irregular, polygonal pores. Thorax flatly campanulate, with subregular, hexagonal pores, and six stout radial ribs; the lateral connected in pairs. (Fig. 6 exhibits the central part of the shell, seen from below.) In the subcircular collar septum the two anterior (jugular) meshes are much smaller than the two posterior (cardinal) meshes. The odd anterior (sternal) rib is opposite to the posterior (caudal) rib. The two paired ribs of each side (antero-lateral or pectoral and postero-lateral or ventral ribs) diverge from one common point. In the specimen figured the left half of the thorax exhibited the two regular ribs, and the right half three, a posterior accessory branch being developed (transition to Octophormis). This specimen might indeed be called Heptaphormis heptalactis.

Dimensions.—Cephalis 0.02 long, 0.05 broad; thorax 0.08 long, 0.22 broad.

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

7. Sethophormis hexagonalis, n. sp.

Cephalis small, flat, cap-shaped, with small, regular, hexagonal pores. Thorax flatly conical, nearly discoidal, with larger pores of the same form, and six stout, straight, prominent ribs. These arise at equal distances from the six corners of the hexagonal base of the collar septum. Peristome hexagonal, with a corona of short spines.

Dimensions.—Cephalis 0.015 long, 0.04 broad; thorax 0.06 long, 0.24 broad.

Habitat.—North Atlantic, Station 354, surface.

Subgenus 4. Octophormis, Haeckel.

Definition.—Thorax with eight radial ribs, four secondary interradial beams being interpolated between the four primary perradial beams of Tetraphormis.

8. Sethophormis octalactis, n. sp.

Cephalis large, hemispherical, with irregular, polygonal pores. Thorax flatly campanulate, with regular, hexagonal pores, and eight stout, regularly-disposed, radial ribs reaching the margin at equal distances. Four of these correspond to the four primary ribs of Tetraphormis cruciata, and exhibit at their base a larger pair of basal pores, surrounded by a semicircular ring (Pl. 70, fig. 5); the other four are secondary, interpolated. Peristome circular, simple.

Dimensions.—Cephalis 0.03 long, 0.06 broad; thorax 0.1 long, 0.22 broad.

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

Subgenus 5. Enneaphormis, Haeckel, 1881, Prodromus, p. 432.

Definition.—Thorax with nine radial ribs, three of which are the primary beams, the other six being secondary and interpolated.

9. Sethophormis rotula, n. sp. (Pl. 57, fig. 9).

Enneaphormis rotula, Haeckel, 1881, Prodromus et Atlas, pl. lvii. fig. 9.

Cephalis very large, flat, cap-shaped, trilobed, with irregular, polygonal network. Horizontal collar-ring stout, hexagonal, with three larger and three alternate smaller sides of half the length. From the middle of the three larger sides arise three horizontal, centripetal, radial beams, which are united in the centre of the collar-septum—the three primary cortinar beams. These are prolonged outside into three centrifugal primary ribs of the thorax. From the six corners of the collar-ring arise six other secondary, thoracic ribs, equal in size and similar in form to the three primary. Each of these nine equal, straight ribs of the thorax is thickened towards the distal end, and bears at equal distances five pairs of opposite (tangential) lateral branches. The opposite branches of the neighbouring spines become united, and lie nearly horizontally in one plane, so that the flat, discoidal thorax is like a nine-angled wheel with nine equally distant spokes and five concentric, nine-angled rings.

Dimensions.—Cephalis 0.12 diameter, thorax 0.36 diameter.

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

10. Sethophormis triloba, n. sp.

Cephalis large, hemispherical, distinctly trilobed, with dense, irregular, polygonal network. From the centre of its top diverge three stout arches or semilunar rods, which are curved downwards, and unite with the three horizontal, radial beams of the collar-septum inside the collar-ring. These three parietal arches of the cephalis are much stronger than in the similar preceding species (Pl. 57, fig. 9), and between them are placed three vaulted bosoms of the cephalis. The collar-ring and the thorax are of the same form as in the preceding, but possess only four concentric, nine-angled rings.

Dimensions.—Cephalis 0.05 long, 0.08 broad; thorax 0.24 diameter.

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

11. Sethophormis enneastrum, n. sp.

Cephalis very large, flat, cap-shaped, with hexagonal base, trilobed, of similar form and structure to the two preceding species. The flat, discoidal thorax has also the same form, with nine stout ribs and five concentric, nine-angled rings; its forty-five large meshes, however, are not so simple as these (Pl. 57, fig. 9), but are subdivided into irregular, smaller meshes by interpolated radial beams connecting the concentric rings.

Dimensions.—Cephalis 0.1 diameter, thorax 0.3 diameter.

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

12. Sethophormis arachnium, n. sp.

Cephalis very large, flat, cap-shaped, trilobed, with hexagonal base, of the same structure as in the three preceding species. The flat discoidal thorax is also similar, and has the same structure as in the preceding species (Pl. 57, fig. 9); but the number of concentric, nine-angled rings is raised from five to eight, and in its outer part nine secondary radial beams are interpolated between the nine primaries, so that the peristome has not nine but eighteen corners.

Dimensions.—Cephalis 0.08 diameter, thorax 0.4 diameter.

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

13. Sethophormis enneactis, n. sp.

Cephalis small, hemispherical, with small, irregular, polygonal pores. Thorax flatly pyramidal, nearly discoidal, with nine prominent, stout ribs, which are connected by numerous (twelve to sixteen) horizontal, nine-angled rings. In the outer half of the thorax there are nine weaker secondary ribs interpolated between the nine stronger primaries, and eighteen shorter and feebler tertiary ribs between the former and the latter. Peristome denticulated, nine-angled.

Dimensions.—Cephalis 0.03 diameter, thorax 0.08 long, 0.24 broad.

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

14. Sethophormis eupilium, n. sp. (Pl. 56, fig. 9).

Sethopyramis eupilium, Haeckel, 1882, Atlas, pl. lvi. fig. 9.

Craspedilium eupilium, Haeckel, 1878, Manuscript.

Cephalis very small, hemispherical, hyaline, without pores. Thorax flatly pyramidal, with nine concave, triangular faces and nine little curved, stout, radial beams. Between these are interpolated numerous incomplete secondary beams, which are absent in the apical part of the thorax. The radial beams being connected by numerous (thirty to forty or more) horizontal, ring-like threads, a delicate arachnoidal network with small, quadrangular pores is produced. Peristome nine-angled, with a peculiar vertical gallery, composed of four horizontal, parallel, nine-angled rings, which are connected by numerous vertical, parallel bars, therefore with three transverse rows of square pores. This peculiar species is very different from the preceding and may represent a separate genus, Craspedilium.

Dimensions.—Cephalis 0.01 diameter, thorax 0.1 long, 0.25 broad.

Habitat.—Central Pacific, Station 271, surface.

Subgenus 6. Astrophormis, Haeckel.

Definition.—Thorax with a variable number of radial ribs (twelve to twenty or more).

15. Sethophormis aurelia, n. sp. (Pl. 55, figs. 3, 4).

Leptarachnium aurelia, Haeckel, 1879, Manuscript et Atlas.

Cephalis large, nearly hemispherical, with irregular, delicate network of small square meshes. Collar-septum with four large meshes, separated by a cross of four bars, opposite in pairs. Thorax flatly campanulate, with delicate, subregular, hexagonal meshes, and twenty-four prominent radial ribs; four of these are primary or perradial (centrifugal prolongations of the four bars of the collar-septum); four others are interradial or secondary, alternating with the former at angles of 45°; sixteen others are adradial or tertiary, interpolated between the first and second more or less irregularly. In some specimens the disposition of the twenty-four ribs was more regular, in others more irregular, than in the specimen figured (figs. 3, 4). The central capsule (fig. 4) exhibits a flat, cap-shaped part with the nucleus (enclosed in the cephalis), and four large, pear-shaped lobes protruded through the four large collar holes (somewhat deformed in the preparation figured). The wall of the thorax exhibits at the base four larger, nearly semicircular pores, bisected by the four primary thoracic ribs. Peristome with twenty-four indentations (between the prominent distal ends of the twenty-four ribs), often more distinct than in the specimen figured.

Dimensions.—Cephalis 0.03 long, 0.08 broad; thorax 0.1 to 0.2 long, 0.4 to 0.6 broad.

Habitat.—Central Pacific, Station 263 to 274, depth 2350 to 2925 fathoms.

16. Sethophormis dodecaster, n. sp. (Pl. 56, fig. 12).

Cephalis small, flatly cap-shaped, with irregular, small, roundish pores. Thorax flatly conical, nearly of the same shape as in the preceding species, but only with twelve prominent ribs; four primary or perradial ribs (as prolongations of the four crossed cortinar bars), and eight adradial ribs interpolated between the former, and arising at some distance from the collar ring. Peristome with twelve prominent pointed lobes (supported by the distal ends of the twelve ribs), and with twelve semicircular bosoms between them. (The specimen figured is young and not fully developed.)

Dimensions.—Cephalis 0.02 long, 0.04 broad; thorax 0.1 long, 0.3 broad.

Habitat.—South Pacific, Station 298, depth 2225 fathoms.

17. Sethophormis umbrella, n. sp. (Pl. 70, figs. 4, 5).

Cephalis large, flatly cap-shaped, with irregular, small polygonal meshes. Thorax flat, umbrella-shaped, with subregular, hexagonal meshes, and sixteen strong radial ribs. Four of these are perradial, and centrifugal prolongations of the four crossed collar beams; four others are interradial, and arise, alternating with the former, directly from the horizontal collar ring; eight ribs are adradial or tertiary, and arise in pairs from the four large perradial basal arches of the thorax, which become bisected by the four primary ribs. Peristome irregularly denticulate.

Dimensions.—Cephalis 0.02 long, 0.06 broad; thorax 0.12 long, 0.32 broad.

Habitat.—North Pacific (off Japan), Stations 236 to 239, surface.

18. Sethophormis floscula, n. sp.

Cephalis small, hemispherical, with subregular, small hexagonal pores. Thorax flatly conical, with larger hexagonal meshes and twenty-four ribs; four of these are perradial and prolongations of the four collar bars; four interradial arise from the collar ring between the former, alternating with them. Each of these eight main ribs gives off two more or less irregular, lateral branches (one at each side), altogether sixteen. The thorax is similar to Cladarachnium ramosum (Pl. 55, fig. 5), whilst the cephalis is quite different. Peristome with twenty-four prominent triangular lobes.

Dimensions.—Cephalis 0.02 long, 0.03 broad; thorax 0.1 long, 0.4 broad.

Habitat.—South Atlantic, Station 325, surface.

19. Sethophormis leptoscenium, n. sp.

Cephalis very small, spherical, with few small, circular pores. Thorax flatly conical or tent-shaped, with concave lateral outlines, small hexagonal meshes, and numerous (thirty to forty or more) strong, little curved, simple radial ribs. Peristome nearly circular, with a corona of small, irregular, conical spines.

Dimensions.—Cephalis 0.015 diameter; thorax 0.07 long, 0.26 broad.

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

20. Sethophormis leptopilium, n. sp.

Cephalis very small, subspherical, hyaline, without pores. Thorax flatly conical or hat-shaped, with concave lateral outlines, and a very delicate network of small square meshes (similar to Litharachnium araneosum, Pl. 55, fig. 8). This is supported by thirty-two curved radial ribs, four of which are primary, four secondary, and the other twenty-four interpolated. Peristome horizontally expanded and little recurved, like the reflexed brim of a hat.

Dimensions.—Cephalis 0.12 diameter; thorax 0.08 long, 0.24 broad.

Habitat.—South Pacific, Station 291, depth 2250 fathoms.

Genus 559. Sethamphora,^[176] n. gen.

Definition.—Sethophormida (vel Dicyrtida multiradiata aperta) with numerous curved ribs in the wall of the ovate thorax, the small mouth of which is constricted. Cephalis without horn.

The genus Sethamphora differs from the preceding Sethophormis, and from the next following ribbed Sethophormida, mainly in the small, more or less constricted mouth; therefore the thorax is more or less ovate, and its ribs curved, with the convexity external. Sethophormis may be divided into two different subgenera, Dictyoprora and Cryptocephalus; in the former the cephalis is perfectly free and well developed, in the latter it is more or less hidden in the uppermost part of the thorax (like Carpocanium).

Subgenus 1. Dictyoprona, Haeckel, 1881, Prodromus, p. 430.

Definition.—Cephalis large, perfectly free, not hidden in the thorax.

1. Sethamphora hexapleura, n. sp.

Shell ovate, smooth, with distinct collar stricture. Length of the two joints = 3 : 11, breadth = 5 : 10. Cephalis large, free, hemispherical, with small circular pores. Thorax truncate, ovate, with six strong curved ribs, and six large triangular meshes between them in the upper half; five smaller pores between every two ribs in the lower half (in three tiers); therefore, together, thirty-six thoracic meshes. Mouth strongly constricted, smooth, only one-third as broad as the thorax.

Dimensions.—Cephalis 0.03 long, 0.05 broad; thorax, 0.11 long, 0.1 broad.

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

2. Sethamphora enneapleura, n. sp.

Shell subovate, smooth, with slight collar stricture. Length of the two joints = 3 : 9, breadth = 4 : 8. Cephalis large, hemispherical, free, with small circular pores. Thorax inflated, ovate, with nine strong curved ribs, which are connected by five transverse circular rings at equal distances. Forty-five rounded, squarish, large meshes between them, in five transverse and nine longitudinal rows. Mouth constricted, smooth, half as broad as the thorax.

Dimensions.—Cephalis 0.03 long, 0.04 broad; thorax 0.09 long, 0.08 broad.

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

3. Sethamphora dodecapleura, n. sp.

Shell urceolate, smooth, with sharp collar stricture. Length of the two joints = 3 : 9, breadth = 5 : 9. Cephalis flat, cap-shaped, free, with twelve ribs, and very small pores between them. Thorax thick-walled, inflated, with subcylindrical cavity, and twelve prominent sharp ribs, alternating with twelve longitudinal rows of very small circular pores (eight pores in each row). Mouth constricted, half as broad as the thorax.

Dimensions.—Cephalis 0.03 long, 0.05 broad; thorax 0.09 long, 0.09 broad.

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

4. Sethamphora mongolfieri, Haeckel.

Eucyrtidium mongolfieri, Ehrenberg, 1854, Mikrogeol., Taf. xxxiv. fig. 18; Abhandl. d. k. Akad. d. Wiss. Berlin, 1875, p. 72, Taf. x. fig. 3.

Shell urceolate, smooth, with distinct collar stricture. Length of the two joints = 2 : 9, breadth = 3 : 7. Cephalis campanulate, with eighteen ribs and small pores. Thorax nearly ellipsoidal, with eighteen prominent ribs, and eighteen longitudinal rows of regular circular pores between them (eight pores in each row; therefore 144 pores altogether). Mouth constricted, only one-third as broad as the thorax.

Dimensions.—Cephalis 0.02 long, 0.03 broad; thorax 0.09 long, 0.07 broad.

Habitat.—Fossil in Barbados.

5. Sethamphora costata, n. sp. Pl. 62, fig. 3.

Shell urceolate, smooth, very similar to the preceding species; also with eighteen longitudinal ribs, but differing in the larger size of the cephalis and its pores, and in the more slender and ovate form of the thorax. Length of the two joints = 5 : 10, breadth = 5 : 8. Pores of the cephalis more numerous. Mouth half as broad as the thorax.

Dimensions.—Cephalis 0.05 long, 0.05 broad; thorax 0.1 long, 0.08 broad.

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

6. Sethamphora serrata, n. sp.

Shell ovate, spinulate, without external collar stricture. Length of the two joints = 1 : 6, breadth = 2 : 4. Cephalis flat, cap-shaped, with small circular pores. Thorax ovate, truncate, with eighteen serrate longitudinal ribs, alternating with eighteen longitudinal rows of short and broad rather oblong pores (twenty to thirty pores in each row). Mouth strongly constricted, only one-fourth as broad as the thorax.

Dimensions.—Cephalis 0.02 long, 0.04 broad; thorax 0.12 long, 0.08 broad.

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

7. Sethamphora ampulla, Haeckel.

Eucyrtidium ampulla, Ehrenberg, 1854, Mikrogeol., Taf. xxxvi. fig. 15; Abhandl. d. k. Akad. d. Wiss. Berlin, 1875, p. 72, Taf. x. figs. 11, 12.

Shell broad, urceolate, spiny, with sharp collar stricture. Length of the two joints = 1 : 4, breadth = 1 : 5. Cephalis subspherical, with few small pores (in figs. 12a and 12b of Ehrenberg, loc. cit., broken off, so that the four pores of the cortinar septum appear). Thorax inflated, bottle-shaped, with twenty prominent, sharply dentate ribs, alternating with twenty longitudinal rows of circular pores (about eight pores in each row). Mouth flat, constricted, one-third as broad as the thorax.

Dimensions.—Cephalis 0.025 long, 0.03 broad; thorax 0.1 long, 0.14 broad.

Habitat.—Fossil in Barbados.

8. Sethamphora aërostatica, Haeckel.

Podocyrtis aërostatica, Ehrenberg, 1875, Abhandl. d. k. Akad. d. Wiss. Berlin, p. 80, Taf. xvi. fig. 4.

Shell broad, urceolate, smooth, with sharp collar stricture. Length of the two joints = 2 : 6, breadth = 3 : 8. Cephalis hemispherical, large, with few pores (broken off in fig. 4a of Ehrenberg, so that the six collar pores appear). Thorax inflated, bottle-shaped, with twenty-two to twenty-four smooth prominent ribs, alternating with the some number of longitudinal rows of small circular pores. Mouth very small, strongly constricted, scarcely as broad as the cephalis, with three short teeth.

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

Habitat.—Fossil in Barbados.

Subgenus 2. Cryptocephalus, Haeckel, 1881, Prodromus, p. 430.

Definition.—Cephalis more or less hidden in thorax, being partly enveloped by its uppermost part.

9. Sethamphora microstoma, n. sp. (Pl. 57, fig. 5).

Cryptoprora microstoma, Haeckel, Atlas, pl. lvii., fig. 5.

Shell ovate, smooth, without external collar stricture. Length of the two joints = 1 : 6, breadth = 2 : 4. Cephalis flat, cap-shaped, without ribs, with small circular pores. Thorax ovate, with twenty-four prominent ribs, alternating with deep longitudinal furrows, each of which contains a series of about fifteen small circular pores. Mouth very small, representing a short cylindrical tube, which is only one-eighth as broad as the thorax.

Dimensions.—Cephalis 0.02 long, 0.04 broad; thorax 0.12 long, 0.08 broad.

Habitat.—Western Tropical Pacific, Station 220, depth 1100 fathoms.

10. Sethamphora favosa, n. sp, (Pl. 57, fig. 4).

Cryptocephalus favosus, Haeckel, 1881, Prodromus, p. 430.

Shell ovate, dimply. Length of the two joints = 1 : 5, breadth = 1 : 5. Cephalis subspherical, small, completely hidden in the thickened top of the thorax (but very distinct in the longitudinal section). Thorax ovate, with twenty-five to thirty longitudinal ribs, alternating with the same number of longitudinal furrows, each of which contains ten to twelve circular, hexagonally framed pores. In the smooth wall of the peristome only twelve triangular ribs are visible. Mouth constricted, one-third as broad as the thorax.

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

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

Genus 560. Sethopyramis,^[177] Haeckel, 1881, Prodromus, p. 432 (sensu emendato !)

Definition.—Sethophormida (vel Dicyrtida multiradiata aperta) with numerous straight or slightly curved radial ribs in the wall of the pyramidal thorax. Network simple. Cephalis commonly without horn.

The genus Sethopyramis and the four following genera form together a peculiar small group (Sethopyramida), characterised by the slender pyramidal shell, in the wall of which numerous (six to nine or more) radial ribs are enclosed. These ribs may be regarded as the terminal feet of a Calpophæna or Halicalyptra, which become connected by transverse bars. Sethopyramis may be derived also directly from Patagospyris by loss of the primary sagittal ring and reduction of the cephalis.

Subgenus 1. Sestropyramis, Haeckel.

Definition.—Pyramidal shell with six radial main beams (sometimes also five or seven, as individual varieties).

1. Sethopyramis scalaris, Haeckel.

Cornutella scalaris, Ehrenberg, 1875, Abhandl. d. k. Akad. d. Wiss. Berlin, p. 68, Taf. ii. fig. 1.

Shell smooth, slenderly pyramidal, hexagonal. Cephalis large, subglobular, hyaline, without pores (or with very small and scarce pores). Thorax with six straight (or little curved) stout longitudinal ribs or radial beams, which are connected by twenty to thirty complete, hexagonal, horizontal rings. The large meshes so produced are regular, square, their length and breadth equally and gradually increasing towards the mouth.

Dimensions.—Cephalis 0.04 diameter; thorax (with twenty-four transverse rings) 0.4 long, 0.15 broad at the mouth.

Habitat.—Fossil in Barbados.

2. Sethopyramis hexalactis, n. sp.

Shell thorny, of the same form as, and similar structure to, the preceding species, but differing in the spiny surface and the smaller subglobular cephalis, which bears small circular pores and an oblique conical horn twice the length. The whole surface is covered with short conical thorns.

Dimensions.—Cephalis 0.02 diameter; thorax (with twenty transverse rings) 0.25 long, 0.1 broad.

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

Subgenus 2. Cephalopyramis, Haeckel, 1881, Prodromus, p. 432.

Definition.—Pyramidal shell with nine radial main beams (sometimes also eight or ten, as individual varieties).

3. Sethopyramis enneactis, n. sp. (Pl. 56, fig. 7).

Cephalopyramis enneactis, Haeckel, 1881, Prodromus et Atlas, pl. lvi. fig. 7.

Shell smooth, slender, pyramidal. Cephalis large, ovate, with pointed apex, nearly hyaline, with very few and small scattered pores. Thorax very slenderly pyramidal, with straight lateral outlines, and nine stout and straight radial beams, which are connected by fifteen to twenty horizontal complete rings. Meshes subregular, square, simple, without secondary network; their length and breadth equally increasing towards the mouth.

Dimensions.—Cephalis 0.05 long, 0.03 broad; thorax (with twenty transverse rings) 0.24 long, 0.1 broad at the mouth.

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

4. Sethopyramis quadrata, n. sp. (Pl. 54, fig. 2).

Shell smooth, slenderly pyramidal, very similar in form and structure to the preceding species; differing from it in the rudimentary cephalis, which is very small, hemispherical, with few small porules. The three internal cortinar bars of the collar stricture are present; when they become lost this species passes over into Bathropyramis quadrata (Pl. 54, fig. 1).

Dimensions.—Cephalis 0.01 long, 0.02 broad; thorax (with ten transverse rings) 0.15 long, 0.1 broad at the mouth.

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

5. Sethopyramis quadratella, Haeckel.

Cornutella quadratella, Ehrenberg, 1875, Abhandl. d. k. Akad. d. Wiss. Berlin, p. 68, Taf. ii. fig. 2.

Litharachnium quadratella, Bütschli, 1882, Zeitschr. f. wiss. Zool., vol, xxxvi. p. 540, Taf. xxxiii. fig. 37.

Shell smooth, broadly pyramidal. Cephalis ovate, small, blunt, hyaline, with very few and small pores (in the figure of Ehrenberg broken off). Thorax broadly pyramidal, with straight lateral outlines, and nine stout and straight radial beams, which are connected by eight to twelve horizontal complete rings. Meshes in the upper half regular, square, in the lower half broad, rectangular (in the tenth transverse row twice as broad as long).

Dimensions.—Cephalis 0.03 long, 0.02 broad; thorax (with ten transverse rings) 0.15 long, 0.15 broad.

Habitat.—Fossil in Barbados.

6. Sethopyramis trapezoides, n. sp.

Shell smooth, broadly pyramidal. Cephalis large, ovate, hyaline, without pores; its collar septum exhibits distinctly the four collar pores (two larger cardinal and two smaller jugular pores). Thorax broad, pyramidal, with slightly concave lateral outlines and nine (sometimes eight or ten) curved ribs, which are connected by eighteen to twenty-four complete transverse rings. The large meshes, so produced, have the form of a parallel trapezoid, and are in the eighth transverse row three times as broad as long. (Differs from Bathropyramis trapezoides, Pl. 54, fig. 3, mainly by the possession of a well developed cephalis).

Dimensions.—Cephalis 0.04 long, 0.03 broad; thorax (with eighteen rings) 0.32 long, 0.24 broad.

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

7. Sethopyramis spinosa, n. sp.

Shell thorny, slender, pyramidal. Cephalis small, subspherical, with few small pores and a straight, vertical, conical horn twice the length. Thorax with nine straight ribs, which are connected by sixteen to twenty complete transverse nine-angled rings. The large meshes so produced are subregular, square. From each nodal point a short conical spine arises. (Differs from the similar Bathropyramis spinosa, Pl. 54, fig. 4, by the development of the cephalis and the simple pointed, unforked spines.)

Dimensions.—Cephalis 0.03 diameter; thorax (with sixteen rings) 0.2 long, 0.12 broad.

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

8. Sethopyramis hexagonalis, n. sp.

Shell papillate, slender, pyramidal. Cephalis small, hemispherical, with a straight conical horn twice the length, and small circular pores. Thorax conical, with slightly convex outlines and nine stout, somewhat curved ribs in zig-zag form, which are connected by ten to twelve interrupted transverse bars. From each nodal point a small conical papilla arises. The large meshes so produced are regular, hexagonal, gradually increasing in size towards the mouth.

Dimensions.—Cephalis 0.03 diameter; thorax (with twelve transverse rows of meshes) 0.18 long, 0.12 broad.

Habitat.—South Atlantic, Station 335, depth 1425 fathoms.

9. Sethopyramis cyclomma, n. sp.

Shell thorny, slender, pyramidal. Cephalis large, subspherical, with numerous very small circular pores, and a small conical horn of the same length. Thorax similar in form and structure to that of the preceding species; but each hexagonal mesh is provided with a very thin circular hyaline ring (like a diaphragm), so that the openings are not hexagonal, but circular. From each nodal point a short pointed conical or slightly forked spine arises.

Dimensions.—Cephalis 0.02 diameter; thorax (with ten transverse rows of meshes) 0.18 long, 0.14 broad.

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

Subgenus 3. Actinopyramis, Haeckel.

Definition.—Pyramidal shell with twelve or more radial beams (commonly twelve to twenty-four, sometimes forty or more).

10. Sethopyramis dodecalactis, n. sp.

Shell smooth, slender, pyramidal. Cephalis small, spherical, hyaline, with a short conical horn. Thorax with twelve radial ribs in the upper half, between which twelve others are interpolated in the lower half. These are connected by twenty to twenty-four complete transverse rings. The meshes so produced are subregular, rectangular.

Dimensions.—Cephalis 0.03 diameter; thorax 0.6 long, 0.2 broad.

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

11. Sethopyramis bicornis, n. sp.

Shell spiny, slender, pyramidal. Cephalis small, spherical, hyaline, with two divergent conical horns, the major (occipital) three times and the minor (frontal) twice as long. Thorax slender, pyramidal, campanulate, thorny, with twenty to thirty radial beams, which are little curved, convex in the upper, concave in the lower half, and connected by numerous interrupted transverse bars. Meshes in the upper third rounded, in the lower two-thirds quadrangular, of very different sizes. Surface covered with spinules.

Dimensions.—Cephalis 0.02 diameter; thorns 0.9 long, 0.4 broad.

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

12. Sethopyramis maxima, n. sp.

Shell smooth, slender, pyramidal. Cephalis small, spherical, with few small pores, and a stout, vertical, conical horn twice the length. Thorax very prolonged, conical, with straight lateral outlines and numerous (twenty to fifty) radial beams (in the upper third twelve, in the middle third twenty-four, in the lower third forty to fifty, by interpolation); they are connected by very numerous interrupted transverse bars. Meshes subregular, quadrangular. Surface smooth.

Dimensions.—Cephalis 0.02 diameter; thorax 1.05 long, 0.45 broad.

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

Genus 561. Plectopyramis,^[178] Haeckel, 1881, Prodromus, p. 432.

Definition.—Sethophormida (vel Dicyrtida multiradiata aperta) with numerous straight or slightly curved radial ribs in the wall of the pyramidal thorax. Network double, the large primary meshes being fenestrated by fine secondary network. Cephalis commonly without horn.

The genus Plectopyramis differs from the preceding Sethopyramis, its ancestral form, only in the peculiar double fenestration of the shell, the large primary meshes of which are separated by strong bars, and filled up by a very delicate arachnoidal network, composed of small pores and very thin threads between them. This double lattice-work often exhibits a very remarkable regularity. As in the preceding genus, the number of radial ribs is commonly six or nine, rarely twelve to twenty or more.

Subgenus 1. Hexapleuris, Haeckel.

Definition.—Pyramidal shell with six radial main beams (sometimes five or seven in individual varieties).

1. Plectopyramis magnifica, Haeckel.

Polycystina magnifica, Bury, 1862, Polycystins of Barbados, pl. xi. fig.

Shell smooth, slender, pyramidal. Cephalis large, ovate, pointed, separated from the thorax by a very deep collar stricture, with few irregular pores. Thorax with six strong and straight radial beams, which are connected by about twenty horizontal, hexagonal rings. The large meshes so produced are regular, square, and filled up by an extremely delicate secondary arachnoidal network, composed of regular square pores (as in Pl. 54, figs. 7, 8).

Dimensions.—Cephalis 0.06 long, 0.04 broad; thorax (with twenty transverse rings) 0.4 long, 0.12 broad.

Habitat.—Fossil in Barbados.

2. Plectopyramis hexapleura, n. sp.

Shell thorny, slender, pyramidal. Cephalis large, ovate, blunt, with deep collar stricture. Thorax with six strong and straight radial beams, which are connected by numerous (twenty to thirty) interrupted transverse bars. The large meshes so produced are irregular, quadrangular, and filled up by irregular, delicate, secondary network, with small polygonal pores.

Dimensions.—Cephalis 0.05 long, 0.03 broad; thorax 0.3 long, 0.1 broad.

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

Subgenus 2. Enneapleuris, Haeckel.

Definition.—Pyramidal shell with nine radial main beams (sometimes eight or ten in individual varieties).

3. Plectopyramis dodecomma, n. sp. (Pl. 54, fig. 6).

Shell smooth, slenderly pyramidal, with straight outlines. Cephalis conical, obtuse, with thirty-six small square pores (in nine divergent longitudinal rows, each of four pores). Collar septum (between cephalis and thorax) with four distinct collar pores. Thorax pyramidal, with nine very stout and straight angular radial beams, which are connected by ten to fifteen broad horizontal nine-angled rings. Each of the large regular, square meshes so produced contains a very delicate fenestration, with twelve regular, square pores, separated by two transverse and three longitudinal crossed threads. A very regular and remarkable structure.

Dimensions.—Cephalis 0.03 long, 0.02 broad; thorax (with ten rings) 0.2 long, 0.15 broad.

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

4. Plectopyramis quadratomma, n. sp.

Shell smooth, slenderly pyramidal. Cephalis large, ovate, hyaline, with few very small basal pores and deep collar stricture. Thorax pyramidal, with straight outline, and nine very stout and straight radial beams, which are connected by fifteen to twenty horizontal nine-angled rings. Each of the large regular, square meshes so produced is filled up by a very delicate arachnoidal network, with very numerous and small square pores (as in the similar Cinclopyramis infundibulum, Pl. 54, fig. 7, which differs in the loss of the cephalis).

Dimensions.—Cephalis 0.05 long, 0.03 broad; thorax (with fifteen rings) 0.32 long, 0.2 broad.

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

5. Plectopyramis trapezomma, n. sp. (Pl. 54, fig. 8).

Shell smooth, broadly pyramidal, with concave lateral outlines. Cephalis hemispherical, small, with numerous small, circular pores. Thorax pyramidal, with nine stout, concavely curved radial beams, which are connected by twelve to sixteen horizontal nine-angled rings. The large meshes so produced are in the upper half square, in the lower half parallel trapezoid (in the fifteenth ring three times as broad as long), and filled up by a secondary arachnoidal network, with very numerous and small square pores.

Dimensions.—Cephalis 0.015 long, 0.025 broad; thorax (with fifteen rings) 0.22 long, 0.2 broad.

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

6. Plectopyramis polygonomma, n. sp.

Shell smooth, pyramidal, very similar to the preceding species; differing from it in the irregular shape of the delicate polygonal (not tetragonal) secondary network, filling up the large rectangular meshes. The cephalis is larger, hyaline, pear-shaped, pointed, without pores, with a deep collar stricture. The nine radial beams of the thorax are less concave.

Dimensions.—Cephalis 0.04 long, 0.03 broad; thorax (with fifteen rings) 0.3 long, 0.22 broad.

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

7. Plectopyramis heteromma, n. sp.

Shell smooth, slenderly pyramidal, with concave outlines. Cephalis very small, subspherical, with a small oblique, conical horn, and very small, scarce circular pores. Thorax with nine stout concavely curved radial beams, which are connected by numerous (thirty to fifty or more) interrupted transverse bars. The large irregular meshes so produced are filled up by irregular, polygonal, delicate lattice-work.

Dimensions.—Cephalis 0.02 long, 0.02 broad; thorax 0.6 long, 0.3 broad.

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

8. Plectopyramis serrata, n. sp.

Shell thorny, slenderly pyramidal, with straight outlines. Cephalis very small, spherical, with a long oblique, conical horn, and very small circular pores. Thorax with nine stout, straight, regularly serrate ribs or radial beams, which are connected by numerous (twenty to thirty or more) interrupted transverse bars. The latter, being crossed by intercalated and interrupted irregular radial beams, produce a subregular secondary network of rectangular meshes of different sizes.

Dimensions.—Cephalis 0.02 long, 0.02 broad; thorax, 0.3 long, 0.2 broad.

Habitat.—South Pacific, Station 298, depth 2225 fathoms.

9. Plectopyramis fenestrata, Haeckel.

Pyramis fenestrata, Bury, 1862, Polycystins of Barbados, pl. xxi. fig. 8.

Shell thorny, broadly pyramidal, with straight outlines. Cephalis very small, spherical, hyaline. Thorax with nine stout, spinulate, straight ribs or radial beams, which are connected by ten to fifteen transverse bars, which in the upper half are complete rings, in the lower half interrupted, and crossed by irregularly intercalated radial beams. Meshes therefore irregular, quadrangular. All the bars are thorny.

Dimensions.—Cephalis 0.01 diameter; thorax 0.2 long, 0.16 broad.

Habitat.—Tropical Atlantic.

10. Plectopyramis furcata, n. sp.

Shell spiny, slenderly pyramidal, with straight outlines. Cephalis small, spherical, with few small pores. Thorax with nine stout and straight spinulate ribs, which are connected by a variable number of irregular interrupted transverse bars; the large quadrangular meshes so produced are filled up by irregular delicate network. The entire surface of the thorax is covered with short forked spines.

Dimensions.—Cephalis 0.02 diameter; thorax 0.3 long, 0.2 broad.

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

Subgenus 3. Polypleuris, Haeckel.

Definition.—Pyramidal shell with numerous (twelve or more) radial main beams (commonly twelve to eighteen, sometimes twenty to thirty or more).

11. Plectopyramis polypleura, n. sp. (Pl. 56, fig. 8).

Shell smooth, slenderly conical, with straight outlines. Cephalis small, subspherical, with very small dot-like pores, and an oblique conical horn twice the length. Thorax with numerous (twenty to thirty) divergent longitudinal ribs; usually twelve of these radial beams appear as stronger, primary main ribs, and twelve to eighteen other as secondary, feebler, interpolated ribs. They are crossed by numerous (twenty to forty or more) horizontal rings. The large meshes so produced are quadrangular, and partly filled up by a very delicate secondary network, with small square pores.

Dimensions.—Cephalis 0.03 diameter; thorax 0.36 long, 0.24 broad.

Habitat.—Central Pacific, Station 267, depth 2700 fathoms.

12. Plectopyramis lagena, n. sp.

Shell smooth, wine-bottle shaped, or slenderly conical-campanulate, with bent outlines, which are concave in the upper, convex in the lower half. Cephalis very small, spherical, hyaline, without pores. Thorax with twenty-four radial ribs, twelve stronger primary, alternating with twelve feebler secondary. They are crossed by interrupted transverse bars. The irregular quadrangular meshes so produced are filled up by a delicate, irregular, secondary network.

Dimensions.—Cephalis 0.02 diameter; thorax 0.5 long, 0.3 broad.

Habitat.—South Atlantic, Station 335, depth 1425 fathoms.

Genus 562. Spongopyramis,^[179] n. sp.

Definition.—Sethophormida (vel Dicyrtida multiradiata aperta) with numerous straight or slightly curved radial ribs in the wall of the pyramidal thorax. Network spongy. Cephalis commonly without horn.

The genus Spongopyramis has arisen from Sethopyramis by development of an irregular spongy framework around the lattice-shell, and is one of the small number of Cyrtoidea in which the shell-wall exhibits a spongy structure. In both observed species the cephalis is small, but evident.

1. Spongopyramis spongiosa, n. sp. (Pl. 56, fig. 10).

Plectopyramis spongiosa, Haeckel, 1881, Prodromus et Atlas, loc. cit.

Shell partly or entirely enveloped by spongy framework, slender, pyramidal, with rather straight outlines. Cephalis very small, ovate, hyaline. Thorax with nine very stout and nearly straight ribs, which are connected by fifteen to twenty or more irregular, interrupted transverse bars. The irregular quadrangular meshes so produced are filled up by an irregular secondary network, with meshes of very different size and form. The dense spongy envelope, which in the specimen figured covered only half the shell, was complete in another older specimen.

Dimensions.—Cephalis 0.015 long, 0.01 broad; thorax 0.4 long, 0.25 broad.

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

2. Spongopyramis spongoplecta, n. sp.

Shell entirely enveloped by spongy framework, pyramidal, with straight outlines. Cephalis ovate (twice as large as in the preceding species), with small circular pores. Thorax with twelve stout and straight ribs, which are connected by twenty to twenty-five annular, transverse bars. The subregular square meshes so produced are filled up by irregular, spongy network, which envelops the whole shell more loosely than in Spongopyramis spongiosa.

Dimensions.—Cephalis 0.03 long, 0.02 broad; thorax 0.5 long, 0.2 broad.

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

Genus 563. Acanthocorys,^[180] Haeckel, 1881, Prodromus, p. 432.

Definition.—Sethophormida (vel Dicyrtida multiradiata aperta) with numerous radial ribs in the wall of the pyramidal thorax, prolonged into divergent terminal feet. Network simple. Cephalis commonly with several horns.

The genus Acanthocorys and the following nearly allied Arachnocorys possess a near relation to the three preceding pyramidal genera, but differ from them in the terminal prolongation of the radial ribs, which are commonly spiny and form a corona of free feet around the mouth of the thorax. The cephalis is usually much larger than in the three preceding genera, and bears a variable number of radial horns. Therefore these two genera are probably older and nearer to the common ancestral form of the Sethophormida than the preceding genera. It may be derived directly from Dictyophimus by interpolation of three secondary (interradial) ribs between the three primary (perradial) ribs.

Subgenus 1. Acanthocorallium, Haeckel.

Definition.—Thorax with six divergent ribs or radial beams (three primary or perradial alternating with three secondary or interradial).

1. Acanthocorys hexapodia, n. sp.

Cephalis large, ovate, with subregular hexagonal pores, and six strong, conical, simple, divergent horns of the same length. Thorax flat, conical, smooth, with six large triangular basal holes, separated by six strong, prismatic, smooth beams, which are connected only near the distal end by a hexagonal ring of delicate, irregular network. Collar septum with three meshes, separated by the three centripetal prolongations of the three primary ribs.

Dimensions.—Cephalis 0.05 long, 0.04 broad; thorax 0.12 long, 0.24 broad.

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

2. Acanthocorys pristipodia, n. sp.

Cephalis large, hemispherical, with irregular, polygonal pores, and numerous (ten to twenty) bristle-shaped, radiating horns, which are conical at the base, and twice as long. Thorax flatly campanulate, thorny, with six strong, serrate or spinulate, divergent, radial ribs, prolonged into six free conical feet of the same length. Meshes of the thorax irregular, polygonal, a corona of six larger ones at the base. Collar septum with four meshes, shaped as in Pl. 56, fig. 6.

Dimensions.—Cephalis 0.04 long, 0.06 broad; thorax 0.08 long, 0.18 broad.

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

3. Acanthocorys macropodia, n. sp.

Cephalis small, subspherical, with irregular, roundish pores and numerous small, bristle-shaped horns. Length of the two joints = 1 : 2, breadth = 1 : 6. Thorax sexangular, pyramidal, with six very long and straight, widely divergent feet, which are prismatic and spiny, and three to five times as long as the breadth of the shell. Only the upper third of the six ribs is connected by irregular, roundish network, with six large triangular holes at the base. Collar septum with four meshes which have the same relation to the six ribs as in Sethophormis hexalactis (Pl. 56, fig. 6).

Dimensions.—Cephalis 0.025 diameter, thorax 0.05 long, 0.15 broad.

Habitat.—Central Pacific, Station 271, surface.

4. Acanthocorys bütschlii, Haeckel.

? Clathrocanium ehrenbergii, Bütschli, 1882, Zeitschr. f. wiss. Zool., vol. xxxvi. pp. 514, 539, Taf. xxxii. fig. 18, a, b.

Cephalis large, subspherical, with numerous small, circular pores and three to six divergent, slender, apical horns. Thorax flatly conical, smooth, not much larger than the cephalis, with six large, triangular or ovate basal holes between the six ribs. Three of these ribs are primary or perradial, and arise immediately from the collar septum, alternating with three secondary or interradial ribs, which arise more outside. The specimen observed by me exhibited six apical horns, and was more complete than that figured by Bütschli, the six ribs being prolonged over the connecting lattice-girdle into six short, divergent feet.

Dimensions.—Cephalis 0.06 long, 0.06 broad; thorax 0.08 long, 0.1 broad.

Habitat.—Fossil in Barbados.

Subgenus 2. Acanthocoronium, Haeckel.

Definition.—Thorax with nine divergent ribs or radial beams, three of which are primary or perradial, the other six secondary or interradial.

5. Acanthocorys umbellifera, Haeckel.

Arachnocorys umbellifera, Haeckel, 1862, Monogr. d. Radiol., p. 305, Taf. vi. fig. 12.

Cephalis large, ovate, with subregular, circular pores and numerous divergent, simple spines of different lengths. Thorax flatly conical, with nine strong, divergent ribs, which in the distal half are free, in the proximal half connected by numerous transverse beams, forming irregular polygonal meshes. Dorsal face of the thorax armed with scattered ascending spines.

Dimensions.—Cephalis 0.05 long, 0.035 broad; thorax 0.05 long, 0.12 broad.

Habitat.—Mediterranean (Messina); Atlantic, Station 354, surface.

6. Acanthocorys triloba, n. sp.

Cephalis large, campanulate, trilobed, with irregular, roundish pores, numerous spines, and a large pyramidal horn on the top, which is connected by three constricted arches with the base of the horizontal collar beams. From the latter arise as centrifugal prolongations three stout, curved, primary ribs of the flatly vaulted thorax, and each of these gives off at the base two opposite, lateral, secondary ribs. These nine ribs are spiny, and connected by irregular, arachnoidal network.

Dimensions.—Cephalis 0.05 long, 0.07 broad; thorax 0.08 long, 0.18 broad.

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

7. Acanthocorys enneapodia, n. sp.

Cephalis large, ovate, with irregular roundish pores, and numerous divergent, ascending spines. Thorax smooth, conical, little larger, with the same network, and nine larger, triangular holes at the base; with nine straight, equally-disposed ribs, which are prolonged into slender feet twice the length. With these latter alternate nine shorter radial spines, arising from the truncate peristome.

Dimensions.—Cephalis 0.05 long, 0.04 broad; thorax 0.05 long, 0.09 broad.

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

8. Acanthocorys macroceras, n. sp. (Pl. 97, fig. 12).

Cephalis large, hemispherical, spiny, with regular, circular pores, and a very large, cylindrical, vertical horn five times as long as the whole shell. Thorax spiny, campanulate, with irregular, roundish pores and nine strong, curved ribs, prolonged into nine slender, divergent feet twice the length, which are curved, convex in the proximal half and concave in the distal half.

Dimensions.—Cephalis 0.05 long, 0.08 broad; thorax 0.12 long, 0.2 broad.

Habitat.—South Pacific, Station 298, depth 2225 fathoms.

9. Acanthocorys furcata, n. sp.

Cephalis large, subspherical, spiny, with irregular, roundish pores. Thorax flatly conical, thorny, with irregular, polygonal pores, decreasing in size toward the mouth, and with nine straight divergent ribs, which at the peristome are forked and prolonged into eighteen slender, very long, bristle-shaped feet.

Dimensions.—Cephalis 0.045 diameter, thorax 0.07 long, 0.13 broad.

Habitat.—South Atlantic, Station 323, depth 1900 fathoms.

Subgenus 3. Acanthocorythium, Haeckel.

Definition.—Thorax with a variable number (ten to twenty or more) radial ribs, prolonged into free terminal feet.

10. Acanthocorys dodecaster, n. sp.

Cephalis small, subspherical, with small circular pores and a large conical horn of twice the length, and some accessory spines. Thorax thorny, flatly campanulate, with twelve stout curved ribs, which at the peristome are prolonged into twelve slender, curved feet of twice the length; four of them are centrifugal prolongations of the four cortinar beams separating the four large meshes of the collar septum; eight other ribs are secondary, interpolated in pairs between the former. At the base of the thorax are twelve large triangular holes between the ribs; the other network is irregular, with polygonal meshes.

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

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

11. Acanthocorys polypodia, n. sp.

Cephalis small, hemispherical, with small, roundish pores and divergent radial spines. Thorax flatly conical, spiny, with twenty to twenty-four divergent, straight ribs, which in the proximal third are separated by the same number of large, triangular meshes, in the middle third connected by irregular network, in the distal third free.

Dimensions.—Cephalis 0.02 long, 0.03 broad; thorax 0.06 long, 0.15 broad.

Habitat.—Central Pacific, Station 273, depth 2350 fathoms.

Genus 564. Arachnocorys,^[181] Haeckel, 1860, Monatsber. d. k. preuss. Akad. d. Wiss. Berlin, p. 837.

Definition.—Sethophormida (vel Dicyrtida multiradiata aperta) with numerous radial ribs in the wall of the pyramidal thorax, prolonged into divergent terminal feet. Network double, with an arachnoidal outer mantle around the inner lattice-shell. Cephalis commonly with numerous horns.

The genus Arachnocorys has been derived from the preceding Acanthocorys, by development of numerous external siliceous threads which connect the radial horns of the cephalis with the secondary spines arising from the thoracic ribs. In this way there becomes formed an outer arachnoidal framework, enveloping loosely, like a delicate mantle, the inner primary lattice-shell.

Subgenus 1. Arachnocorallium, Haeckel.

Definition.—Thorax with six divergent ribs or radial beams (three primary or perradial, alternating with three secondary or interradial).

1. Arachnocorys hexaptera, n. sp.

Arachnocorys circumtexta (juv.?), R. Hertwig, 1879, Organism. d. Radiol., p. 79, Taf. viii. fig. 2a.

Cephalis large, subspherical, with irregular, polygonal pores, and numerous bristle-shaped spines twice the length; on the centre of the top a single larger vertical horn. Thorax flatly conical, with six strong and straight widely divergent ribs, which in the proximal half are separated by six large holes, in the distal half connected by a broad ring of irregular network. From each rib arises a perpendicular branch, and these branches are connected together, and with the spines of the cephalis, by arachnoidal network.

Dimensions.—Cephalis 0.04 diameter, thorax 0.08 long, 0.24 broad.

Habitat.—Central Pacific, Station 266; Mediterranean, surface.

2. Arachnocorys discoides, n. sp.

Cephalis small, pyramidal, with irregular, roundish pores and numerous thin spines, on the top a single larger vertical horn. Thorax very flat, nearly discoidal, with six strong and straight ribs, which by communication of few larger and numerous smaller branches form an irregular network with polygonal meshes. From each of the six ribs arise two or three larger, perpendicular branches of half the length, and from the network numerous smaller spines. All these dorsal spines of the shell are connected by a dense arachnoidal wicker-work.

Dimensions.—Cephalis 0.02 diameter, thorax 0.04 long, 0.3 broad.

Habitat.—Central Pacific, Station 271, surface.

Subgenus 2. Arachnocoronium, Haeckel.

Definition.—Thorax with nine divergent ribs or radial beams, three of which are primary or perradial, the other six secondary or interradial. (Sometimes eight or ten occur instead of the nine normal ribs.)

3. Arachnocorys circumtexta, Haeckel.

Arachnocorys circumtexta, Haeckel, 1862, Monogr. d. Radiol., p. 304, Taf. vi. figs. 9-11.

Arachnocorys circumtexta, R. Hertwig, 1879, Organism. d. Radiol., p. 78, Taf. viii. fig. 2.

Cephalis large, subspherical, with numerous roundish pores, and eight to ten slender, conical horns twice the length. Thorax flatly conical, with nine strong, straight, widely divergent, conical feet, each of which bears in the middle of its outer side a perpendicular ascending branch of half the length. These branches and the horns of the cephalis are connected by very thin, parallel, arachnoidal threads. Network of the thorax irregular, with nine larger triangular holes at the base. Collar septum with numerous, irregular, roundish pores.

Dimensions.—Cephalis 0.04 to 0.05 diameter, thorax 0.08 to 0.12 long, 0.15 to 0.25 broad.

Habitat.—Mediterranean (Messina); Atlantic, Stations 347 to 354, surface.

4. Arachnocorys enneaptera, n. sp.

Cephalis large, campanulate, with irregular, polygonal pores, two larger stout pyramidal and numerous slender, bristle-shaped horns. Thorax of the same structure as in the preceding species, only the nine basal holes are of twice the size; the lower network denser (as in Clathrocanium diadema, Pl. 64, fig. 2). Collar septum with numerous, irregular, roundish pores.

Dimensions.—Cephalis 0.05 diameter, thorax 0.12 long, 0.22 broad.

Habitat.—Tropical Atlantic, Station 338, surface.

5. Arachnocorys araneosa, n. sp. (Pl. 56, fig. 11).

Cephalis large, subspherical, with circular, subregular, hexagonally framed pores, and twenty to thirty slender, cylindrical, straight radial spines. Thorax flatly conical, nearly of the same shape as in the two preceding species, but with nine longer ribs, and more irregular, broader network between them. From the middle of each rib arises, nearly horizontally, a strong branch, which is directed outwards. These branches are connected with the spines of the cephalis as well as with the distal half of the ribs, by dense and delicate arachnoidal network, composed of parallel, very thin, siliceous threads (in fig. 11 only partially represented). Collar septum with numerous irregular, roundish pores.

Dimensions.—Cephalis 0.04 diameter, thorax 0.1 long, 0.2 broad.

Habitat.—Central Pacific, Station 270 to 274, surface.

6. Arachnocorys arachnodiscus, n. sp.

Cephalis small, campanulate, conical, with a single very large conical central horn, and numerous smaller accessory spines. Thorax in form and structure similar to that of the three preceding species, but much flatter, being nearly discoidal. The meshes of the network are smaller and more numerous, irregularly polygonal, and the nine basal holes little larger. Collar septum with four large meshes (as in Pl. 60, fig. 6).

Dimensions.—Cephalis 0.25 long, 0.3 broad; thorax 0.04 long, 0.24 broad.

Habitat.—North Pacific, Station 248, surface.

7. Arachnocorys trifida, n. sp.

Cephalis large, campanulate, with irregular, roundish pores and numerous ramified spines; in the centre of the top a larger pyramidal oblique horn of twice the length. Thorax cap-shaped, flatly vaulted, with nine strong convex ribs, prolonged into slender free feet. Three of these nine ribs are the centrifugal prolongations of the three cortinar bars (united in the centre of the collar stricture, separating its three large cortinar meshes); the other six are diverging lateral branches of the former, arising in pairs at both sides of its base. All nine ribs are connected by delicate arachnoidal network with irregular polygonal meshes. From its surface arise thin bristles, and from the base of each main rib a stout, perpendicular branch. All these dorsal spines are connected by irregular, arachnoidal wicker-work, covering thorax and cephalis. (A remarkable primitive species?)

Dimensions.—Cephalis 0.05 long, 0.06 broad; thorax 0.07 long, 0.18 broad.

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

Subgenus 3. Arachnocorythium, Haeckel.

Definition.—Thorax with a variable number of radial ribs (twelve to twenty or more), prolonged into free terminal feet.

8. Arachnocorys polyptera, n. sp.

Cephalis large, subspherical, with irregular, roundish pores and numerous radial spines. Thorax flatly conical, with numerous radial ribs (twenty to thirty), which are in the distal half free, in the proximal half connected by delicate arachnoidal wicker-work, with polygonal, irregular meshes. From its dorsal face arise numerous radial spines, which are connected together, and with the cephalic spines, by very thin and numerous threads, parallel between every two spines. Similar to Arachnocorys araneosa (Pl. 56, fig. 11), but differing in the structure of the cephalis, and in the greater number of the ribs and spines.

Dimensions.—Cephalis 0.04 diameter, thorax 0.12 long, 0.24 broad.

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

Genus 565. Anthocyrtoma,^[182] n. gen.

Definition.—Sethophormida (vel Dicyrtida multiradiata aperta) without thoracic ribs, with six terminal feet around the mouth. Cephalis free, with an apical horn.

The genus Anthocyrtoma and the four following genera form together the peculiar group of Carpocanida, comprising all those Sethophormida in which the original thoracic ribs are lost, and only the terminal feet remain. Anthocyrtoma is the simplest form of this group, possessing only six terminal feet, three primary perradial, and three alternating, secondary, interradial. It may be directly derived either from Lychnocanium, by interpolation of three interradial feet, or from Hexaspyris by loss of the sagittal ring.

1. Anthocyrtoma serrulata, Haeckel.

Anthocyrtis serrulata, Ehrenberg, 1875, Abhandl. d. k. Akad. d. Wiss. Berlin, p. 66, Taf. vi. fig. 7.

Shell pear-shaped, rough, with obliterated collar stricture. Length of the two joints = 1 : 4, breadth = 1 : 3. Cephalis ovate, with very small pores, and a stout conical horn of the same length. Abdomen inflated, truncate, with larger, regular, circular pores, twice as broad as the constricted mouth. Six feet vertical, parallel, serrate, all of the same size, about as long as the cephalis.

Dimensions.—Cephalis 0.06 long, 0.05 broad; thorax 0.2 long, 0.17 broad.

Habitat.—Fossil in Barbados.

2. Anthocyrtoma alterna, n. sp.

Shell pear-shaped, smooth, with distinct collar stricture. Length of the two joints = 1 : 5, breadth = 1 : 6. Cephalis hemispherical, with a slender conical horn of twice the length. Abdomen inflated, subglobular, with regular, circular, hexagonally framed pores, three times as broad as the narrow, constricted mouth. Six feet conical, smooth, somewhat divergent, alternating, of different sizes; the three larger (perradial) half as long as the shell, and twice as long as the three smaller (interradial). (Similar to Anthocyrtis ventricosa.)

Dimensions.—Cephalis 0.03 long, 0.04 broad; thorax 0.15 long, 0.18 broad.

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

Genus 566. Anthocyrtis,^[183] Ehrenberg, Monatsber. d. k. preuss. Akad. d. Wiss. Berlin, 1847, p. 54.

Definition.—Sethophormida (vel Dicyrtida multiradiata aperta) without thoracic ribs, with nine terminal feet around the mouth. Cephalis free, with an apical horn.

The genus Anthocyrtis (in the original definition of Ehrenberg) contained all Dicyrtida without thoracic ribs, with terminal feet. We here restrict the definition to those Sethophormida in which the number of free terminal feet is constantly nine (three primary perradial and three alternate pairs of secondary interradial feet). Anthocyrtis may be derived either directly from Patagospyris by loss of the sagittal ring, or from Lychnocanium by interpolation of three secondary feet.

Subgenus 1. Anthocyrtella, Haeckel.

Definition.—Feet of the peristome-corona divergent, their basal distance less than their terminal distance.

1. Anthocyrtis mespilus, Ehrenberg.

Anthocyrtis mespilus, Ehrenberg, 1854, Taf. xxxvi. fig. 13; Abhandl. d. k. Akad. d. Wiss. Berlin, 1875, p. 66, Taf. vi. fig. 4 (not 5).

Shell smooth, with distinct collar stricture. Length of the two joints = 1 : 5, breadth = 2 : 6. Cephalis hemispherical, with a stout pyramidal horn of twice the length. Thorax nearly hemispherical, with regular, circular, quincuncial pores. Mouth scarcely constricted, with nine divergent, triangular, lamellar feet, about as long as the thorax.

Dimensions.—Cephalis 0.012 long, 0.02 broad; thorax 0.05 long, 0.06 broad.

Habitat.—Fossil in Barbados.

2. Anthocyrtis furcata, Ehrenberg.

Anthocyrtis furcata, Ehrenberg, 1875, Abhandl. d. k. Akad. d. Wiss. Berlin, p. 64, Taf. vi. fig. 2.

Shell smooth, with deep collar stricture. Length of the two joints = 1 : 5, breadth = 2 : 6. Cephalis hemispherical, with a short pyramidal horn of half the length. Thorax hemispherical, with large, irregular, roundish pores. Mouth scarcely constricted, with nine divergent, curved, slender feet, which are about as long as the shell, and forked at the distal end.

Dimensions.—Cephalis 0.01 long, 0.02 broad; thorax 0.05 long, 0.06 broad.

Habitat.—Fossil in Barbados.

3. Anthocyrtis butomus, n. sp.

Shell thorny, with obliterated collar stricture. Length of the two joints = 2 : 6, breadth = 2 : 7. Cephalis ovate, with very small and scarce pores, and a conical horn of the same length. Thorax inflated, pear-shaped, with regular, circular, quincuncial pores. Mouth about half as broad, constricted, with nine divergent, broad, nearly square, lamellar feet, half as long as the thorax (similar to Anthocyrtis serrulata, Ehrenberg, loc. cit., Taf. vi. fig. 7).

Dimensions.—Cephalis 0.05 long, 0.04 broad; thorax 0.12 long, 0.14 broad.

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

4. Anthocyrtis ventricosa, Ehrenberg.

Anthocyrtis ventricosa, Ehrenberg, 1875, Abhandl. d. k. Akad. d. Wiss. Berlin, p. 66, Taf. viii. fig. 1.

Shell thorny, with obliterated collar stricture. Length of the two joints = 1 : 7, breadth = 2 : 7. Cephalis hemispherical, hyaline, without pores, with a slender, conical horn, of about the same length. Thorax inflated, pear-shaped or subspherical, with regular, circular, quincuncial pores. Mouth only one-third as broad, much constricted, with nine divergent, slender, conical feet, about one-fifth as long as the diameter of the shell (partly broken off in Ehrenberg's figure).

Dimensions.—Cephalis 0.03 long, 0.04 broad; thorax 0.14 long, 0.14 broad.

Habitat.—Tropical Atlantic, Station 338, depth 1990 fathoms; also fossil in Barbados.

Subgenus 2. Anthocyrtissa, Haeckel.

Definition.—Feet of the peristome-corona parallel, vertical; their basal and terminal distances equal.

5. Anthocyrtis ophirensis, Ehrenberg.

Anthocyrtis ophirensis, Ehrenberg, 1872, Abhandl. d. k. Akad. d. Wiss. Berlin, p. 285, Taf. ix. fig. 13.

Shell smooth, with slight collar stricture. Length of the two joints = 2 : 4, breadth = 1 : 5. Cephalis ovate, with irregular, roundish pores, and a pyramidal, excentric, vertical horn of the same length. Thorax campanulate, with delicate network of large, regular, hexagonal pores. Mouth scarcely constricted, with nine parallel, vertical, conical feet, about as long as the cephalis. (In the specimen figured by Ehrenberg only seven feet are represented, two being broken off; two other specimens of this species, captured by Rabbe, exhibited nine regularly disposed feet.)

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

Habitat.—Indian Ocean, Zanzibar (Pullen); Madagascar (Rabbe), surface.

6. Anthocyrtis lauranthus, n. sp.

Shell smooth with slight collar stricture. Length of the two joints = 1 : 3, breadth = 1 : 4. Cephalis ovate, with large, roundish pores, and a conical horn of twice the length. Thorax inflated, campanulate, with regular, circular, hexagonally framed pores. Mouth two-thirds as broad, little constricted, with nine parallel, vertical, broad, lamellar, triangular feet, half as long as the cephalis.

Dimensions.—Cephalis 0.04 long, 0.03 broad; thorax 0.1 long, 0.12 broad.

Habitat.—Central Pacific, Station 266 to 270, depth 2550 to 2925 fathoms.

7. Anthocyrtis grossularia, Ehrenberg.

Anthocyrtis grossularia, Ehrenberg, 1875, Abhandl. d. k. Akad. d. Wiss. Berlin, p. 64, Taf. vi. fig. 6.

Shell spiny, with deep collar stricture. Length of the two joints = 1 : 5, breadth = 1 : 4. Cephalis subspherical, thorny, with a conical horn of the same length. Thorax ovate, spiny, with numerous densely-crowded, subregular, circular pores. Mouth about half as broad, constricted, with nine parallel, vertical, slender, conical feet, about as long as the cephalis.

Dimensions.—Cephalis 0.04 long, 0.05 broad; thorax 0.2 long, 0.18 broad.

Habitat.—Fossil in Barbados.

8. Anthocyrtis subglobosa, n. sp.

Shell spiny, with deep collar stricture. Length of the two joints = 1 : 7, breadth = 1 : 7. Cephalis subspherical, with a conical horn twice the length. Thorax nearly spherical, with small and very numerous, regular, circular pores. Mouth only one-third as broad, constricted, with nine parallel, vertical, square, lamellar feet, about twice as long as the cephalis.

Dimensions.—Cephalis 0.03 long, 0.035 broad; thorax 0.2 long, 0.2 broad.

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

Subgenus 3. Anthocyrtura, Haeckel.

Definition.—Feet of the peristome-corona convergent, their basal distance greater than their terminal distance.

9. Anthocyrtis enneaphylla, n. sp.

Shell smooth, with sharp collar stricture. Length of the two joints = 1 : 6, breadth = 1 : 5. Cephalis subspherical, with a conical horn twice the length, nearly hyaline, with very small and scarce pores. Thorax nearly spherical, with regular, circular, quincuncial pores. Mouth only half as broad, with nine broad, triangular feet, twice as long as the cephalis, and curved inwards, convergent towards the main axis.

Dimensions.—Cephalis 0.02 long, 0.025 broad; thorax 0.11 long, 0.12 broad.

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

10. Anthocyrtis ovata, n. sp. (Pl. 62, fig. 13).

Shell smooth, with slight collar stricture. Length of the two joints = 1 : 5, breadth = 1 : 3. Cephalis ovate, with numerous small pores, and an excentric conical horn of the same length. Thorax ovate, with regular, circular, quincuncial pores. Mouth nearly of the same breadth, scarcely constricted, with nine triangular, widely-separated feet, about as long as the cephalis, and convergent towards the main axis.