Dimensions.—Main axis 0.12, equatorial axis 0.07; meshes 0.004 to 0.02, bars 0.002 to 0.005; spines 0.01 to 0.02.

Habitat.—Atlantic, Eastern Tropical part, Station 346, surface.

Genus 153. Stylartus,^[192] Haeckel, 1881, Prodromus, p. 462.

Definition.—Artiscida with two strong, solid, polar spines, or two bunches of polar spines, opposite on the two poles of the main axis.

The genus Stylartus differs from Artiscus by the production of two large opposite spines in the main axis, starting from both poles of it; sometimes every spine is surrounded by a group of smaller radial spines. The genus is nearly allied to Ellipsoxiphus (p. 295), and differs from it only in the equatorial stricture of the ellipsoidal shell. But it may also be derived from the similar Cyphinus (Pl. 39, fig. 14) by loss of the medullary shell.

Subgenus 1. Stylartella, Haeckel.

Definition.—On each pole of the main axis only one single large spine.

1. Stylartus bipolaris, n. sp. (Pl. 48, fig. 5).

Shell thick walled, rough; both its chambers nearly spherical, with irregular, roundish pores, twice to four times as broad as the bars; eight to ten on the half equator of each chamber. Polar spines very strong, conical, as long as the greatest breadth.

Dimensions.—Length of the shell (without spines) 0.18, greatest breadth 0.13; length of the polar spines 0.13, basal breadth 0.03.

Habitat.—Western Tropical Pacific, Station 224, depth 1850 fathoms.

2. Stylartus bicuspis, n. sp.

Shell thin walled, smooth, with regular, circular pores, twice as broad as the bars; twelve to fourteen on the half equator of each chamber. Polar spines very stout, straight, three-sided pyramidal, half as long as the shell.

Dimensions.—Length of the shell 0.16, greatest breadth 0.12; length of the polar spines 0.08, basal thickness 0.025.

Habitat.—Pacific, central area. Station 266, depth 2750 fathoms.

Subgenus 2. Stylartura, Haeckel.

Definition.—On each pole of the main axis a bunch of several spines.

3. Stylartus palatus, n. sp.

Shell thick walled, thorny, with irregular, roundish pores, twice to three times as broad as the bars; fifteen to eighteen on the half equator of each chamber. On each pole of the main axis a large conical spine, surrounded by a group of ten to fifteen smaller spines, one-third to two-thirds as long as the breadth of the deep equatorial stricture.

Dimensions.—Length of the shell 0.14, greatest breadth 0.09; length of the polar spines 0.03 to 0.06, basal breadth 0.005 to 0.015.

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

4. Stylartus penicillus, n. sp.

Shell thin walled, smooth, with irregular, roundish pores, three to four times as broad as the bars; ten to twelve on the half equator of each chamber. On each pole of the main axis a brush-like bunch of twenty to thirty thin conical radial spines, half as long as the shell.

Dimensions.—Length of the shell 0.15, greatest breadth 0.1; length of the polar spines 0.08, basal breadth 0.005.

Habitat.—Equatorial Atlantic, Station 347, surface.

Genus 154. Cannartus,^[193] Haeckel, 1881, Prodromus, p. 462.

Definition.—Artiscida with two hollow polar tubes (fenestrated cylindrical or conical tubuli, opposite on the two poles of the main axis).

The genus Cannartus differs from Artiscus by the production of two opposite hollow tubes on both poles of the main axis. The cavity of the conical or cylindrical fenestrated tubes communicates freely with that of the shell; the network in both is the same. The distal end of the tubes is nearly always broken off, sometimes closed, with a conical apex. Cannartus can be derived either from Pipettella by a transverse equatorial constriction, or from Cannartiscus by the loss of the medullary shell, or from Artiscus by the production of the polar tubes.

1. Cannartus violina, n. sp. (Pl. 39, fig. 10).

Pores of the shell subregular, circular, twice to three times as broad as the bars; eighteen to twenty on the half meridian, fourteen to sixteen on the half equator. Shell-wall in the "tropical zone" of both halves thickened. Polar tubes nearly cylindrical, about as long as the main axis, distal ends broken off.

Dimensions.—Main axis 0.14, equatorial axis 0.09; meshes 0.008, bars 0.003; length of the polar tubes 0.12, breadth 0.02 to 0.03.

Habitat.—Pacific, central area, Station 268, depth 2900 fathoms.

2. Cannartus bitubulus, n. sp.

Pores of the shell regular, circular, hexagonally framed, of the same breadth as the bars; fourteen to sixteen on the half meridian, ten to twelve on the half equator. Polar tubes cylindrical, longer than the main axis, sulcated, distal ends broken off. (Similar to Pipetta tuba, Pl. 39, fig. 7, but with equatorial stricture and without medullary shell.)

Dimensions.—Main axis 0.16, equatorial axis 0.12; meshes and bars 0.006; length of the polar tubes 0.2, breadth 0.025.

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

3. Cannartus biscottus, n. sp.

Pores of the shell irregular, roundish, twice to three times as broad as the bars; ten to twelve on the half meridian, six to eight on the half equator. Polar tubes conical, shorter than the main axis, with closed apex. (Similar to Cannartidium bicinctum, Pl. 39, fig. 18, but without enclosed medullary shell.)

Dimensions.—Main axis 0.11, equatorial axis 0.07; meshes 0.005 to 0.01, bars 0.003; length of the polar tubes 0.08, breadth on the base 0.03.

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

Family XV. Cyphinida, Haeckel (Pl. 39, figs. 11-19).

Cyphinida, Haeckel, 1881, Prodromus, p. 462.

Definition.—Prunoidea with ellipsoidal twin-shell, divided by an equatorial stricture into two communicating hemiellipsoidal or hemispherical chambers; this external twin-shell (cortical shell) is either simple or double, and encloses one or more internal concentric shells (medullary shells). Central capsule ellipsoidal, commonly with an equatorial constriction.

The family Cyphinida have the same characteristic twin-form of the cortical shell as the Artiscida, but differ from them in the presence of a simple or double internal medullary shell, connected with the cortical shell by radial beams. The fenestrated shell is therefore composed of two or more concentric shells as in the Druppulida, but differs from these in the ring-like equatorial constriction.

The Medullary Shell, in the middle of the central capsule, is either single or double, composed of two concentric shells. As in the Druppulida, the form of the medullary shells is either spherical (Pl. 39, fig. 12a) or lenticular, compressed from both poles of the main axis (Pl. 39, fig. 18a); sometimes the inner medullary shell is spherical, the outer lenticular.

The Radial Beams, which connect the medullary shell with the equatorial constriction of the cortical shell, lie either all in the equatorial plane (Pl. 39, fig. 11) or near it on both sides (Pl. 39, figs. 12a, 18a).

The Cortical Shell is commonly simple (Pl. 39, figs. 12, 18), sometimes composed of two concentric shells (Pl. 39, fig. 13), rarely of three. As in the Artiscida, also in the Cyphinida, from both poles of the main axis solid spines or hollow fenestrated tubes are often developed (Pl. 39, figs. 14, 16-18).

The Central Capsule of the Cyphinida (Pl. 39, fig. 13) is of the same form as in the Artiscida, generally ellipsoidal, but with an equatorial ring-like stricture, which divides it into two equal halves. It encloses the simple or double medullary shell, and is perforated by the radial beams starting from this. From the inner surface of the surrounding cortical shell it is separated by a thicker or thinner jelly-layer, the calymma. (Compare also Taf. xxii. fig. 14 of my Monograph, 1862.)

Synopsis of the Genera of Cyphinida.

Genus 155. Cyphanta,^[194] n. gen.

Definition.—Cyphinida with simple cortical shell and simple medullary shell, without polar spines or tubes.

The genus Cyphanta is the most simple of all Cyphinida, and can be regarded as the common ancestral form of this family. It may be derived phylogenetically from Druppula by a ring-like constriction in the equatorial plane of the ellipsoidal cortical shell, or from Artiscus by secondary formation of a central (spherical or ellipsoidal) medullary shell.

Subgenus 1. Cyphantella, Haeckel.

Definition.—Surface of the cortical shell smooth, without spines or thorns.

1. Cyphanta colpodes, n. sp.

Cortical shell thin walled, with smooth surface; its pores regular, hexagonal, three to four times as broad as the bars; ten to twelve on the half meridian, seven to eight on the half equator. Medullary shell spherical, its diameter one-third of the equatorial axis of the cortical shell. (The cortical shell of this species is nearly identical with the central half of the cortical shell of Panartus diploconus, Pl. 40, fig. 1.)

Dimensions.—Main axis of the cortical shell 0.12, equatorial axis 0.07; meshes 0.013; bars 0.003; diameter of the medullary shell 0.025.

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

2. Cyphanta circopora, n. sp.

Cortical shell thick walled, with smooth surface; pores subregular, circular, twice as broad as the bars; eighteen to twenty on the half meridian, twelve to fourteen on the half equator. Medullary shell spherical, its diameter one-half of the equatorial axis of the cortical shell. (The shell of this species is very similar to that of Cannartiscus amphiconiscus, Pl. 39, fig. 19, but without the polar tubes of that species.)

Dimensions.—Main axis of the cortical shell 0.13, equatorial axis 0.08; meshes 0.007, bars 0.003; diameter of the medullary shell 0.04.

Habitat.—Pacific, central area. Station 266, depth 2750 fathoms.

3. Cyphanta lævis, Haeckel.

Cortical shell thin walled, with smooth surface; pores of it irregular, roundish, of very different size (some very large in the tropical circles of both hemispheres). Pores twice to six times as broad as the bars; ten to twelve on the half meridian, six to eight on the half equator. Medullary shell spheroidal, compressed, its main axis somewhat shorter than its equatorial axis, which attains half the length of that of the cortical shell. (This species may be perhaps identical with Ommatospyris lævis of Ehrenberg, the diagnosis of which is insufficient and figure not given.)

Dimensions.—Main axis of the cortical shell 0.1, equatorial axis 0.06; meshes 0.005 to 0.02, bars 0.002 to 0.04; diameter of the medullary shell 0.03.

Habitat.—Philippine Sea (Ehrenberg), Station 213, depths 2650 and 3300 fathoms.

4. Cyphanta arachnoides, n. sp.

Cortical shell very delicate and thin walled, cobweb-like, with smooth surface; pores irregular, polygonal (mostly pentagonal or hexagonal), eight to ten times as broad as the thread-like bars; ten to twelve on the half meridian, six to eight on the half equator. Medullary shell spheroidal, compressed, its main axis shorter than its equatorial axis, which is about one-third that of the cortical shell. (This species is very similar to the middle part of the shell of Ommatocampe profundissima, Ehrenberg, 1872, Abhandl. d. k. Akad. d. Wiss. Berlin, Taf. viii. fig. 6.)

Dimensions.—Main axis of the cortical shell 0.11, equatorial axis 0.06; meshes 0.01 to 0.02, bars 0.002; diameter of the medullary shell 0.02.

Habitat.—Atlantic, Canary Islands (Lanzerote), surface.

Subgenus 2. Cyphantissa, Haeckel.

Definition.—Surface of the cortical shell spiny, everywhere scattered with numerous thorns or spines.

5. Cyphanta hispida, n. sp.

Cortical shell thick walled, with spiny surface; pores regular, circular, with hexagonal frame, twice as broad as the bars; twelve to fourteen on the half meridian, eight to ten on the half equator. From the corners of the hexagonal frames (between every three pores) arise short, straight, conical radial spines, somewhat longer than the breadth of the pores. Medullary shell subspherical, its diameter about one-third of the equatorial axis of the cortical shell. (The appearance of the cortical shell is the same as that of the middle part of Peripanartus amphiconus, Pl. 40, fig. 5.)

Dimensions.—Main axis of the cortical shell 0.12, equatorial axis 0.07; meshes 0.01, bars 0.005; length of the spines 0.012; diameter of the medullary shell 0.02.

Habitat.—Pacific, central area, Station 274, depth 2750 fathoms.

6. Cyphanta hystrix, n. sp.

Cortical shell thin walled, with thorny surface; pores irregular, roundish, of very unequal size, twice to six times as broad as the bars; twelve to eighteen on the half meridian, eight to thirteen on the half equator. Between the pores irregularly scattered, bristle-like, thin spines about the same size, partly straight, partly oblique, rising from the surface. Medullary shell lenticular, compressed, its equatorial axis one and a half times the length of the main axis, and about half that of the cortical shell.

Dimensions.—Main axis of the cortical shell 0.15, equatorial axis 0.09; meshes 0.004 to 0.02, bars 0.003 to 0.006; length of the spines 0.02; diameter of the medullary shell 0.04.

Habitat.—South Atlantic, Station 318, surface.

Genus 156. Cyphonium,^[195] n. gen.

Definition.—Cyphinida with simple cortical shell and double medullary shell, without polar spines or tubes.

The genus Cyphonium contains a number of very common species, among which are the earliest known forms of this family, partly described by Ehrenberg as Ommatospyris (which genus contains also a number of other Prunoidea), partly by me (1862) as Didymocyrtis. Both names are inadequate, as allusions to quite different families of Nassellaria, but may be retained as significations of subgeneric divisions. Cyphonium differs from Cyphanta by the double medullary shell, which is either spherical or lenticular.

Subgenus 1. Ommatospyris, Ehrenberg (partim).

Definition.—Surface of the cortical shell smooth, without thorns or spines.

1. Cyphonium coscinoides, n. sp.

Cortical shell thin walled, with smooth surface; pores regular, hexagonal, three to four times as broad as the bars; five to six on the half meridian, eight to nine on the half equator of each chamber. Medullary shells both spherical. (The cortical shell of this species is nearly the same as that of Cyphanta colpodes, and as the middle part of the cortical shell of Panartus diploconus, Pl. 40, fig. 1.)

Dimensions.—Main axis of the cortical shell 0.11, equatorial axis 0.06; greatest breadth of the chambers 0.08; pores 0.013, bars 0.003.

Habitat.—North Pacific, Station 244, surface.

2. Cyphonium virgineum, n. sp. (Pl. 39, figs. 12, 12a).

Cortical shell thick walled, with smooth surface (sometimes a little rough with very small thorns); pores subregular, circular, with hexagonal elevated frames, about as broad as the bars; ten to twelve on the half meridian, sixteen to eighteen on the half equator of each chamber. Medullary shells (fig. 12a) both spherical. (Sometimes, as in the figured specimen, the shell is somewhat irregular, an individual abnormality.)

Dimensions.—Main axis of the cortical shell 0.13 to 0.15; equatorial axis of the structure 0.08 to 0.09, of each chamber 0.1 to 0.12, pores and bars 0.005 to 0.007.

Habitat.—Pacific, western tropical part, Station 225, depth 4475 fathoms.

3. Cyphonium ethmarium, n. sp.

Cortical shell thin walled, with quite smooth surface; pores subregular, circular (without hexagonal frame), twice as broad as the bars; nine to ten on the half meridian of each chamber, sixteen to eighteen on its half equator. Medullary shells both spherical. (This species resembles the proximal internal chambers of Peripanartus atractus, Pl. 40, fig. 7.)

Dimensions.—Main axis 0.13, equatorial axis 0.07; greatest breadth 0.09; pores 0.006, bars 0.003.

Habitat.—Equatorial Atlantic, Station 347, surface.

4. Cyphonium trinacrium, n. sp.

Cortical shell thick walled, with rough surface; pores subregular, circular (without hexagonal frame), not broader than the bars; five to six on the half meridian of each chamber, nine to ten on its half equator. Medullary shells both compressed, lenticular. This species resembles Cypassis entomocora vel Ommatocampe trinacria, Stöhr, 1880, loc. cit., p. 90, Taf. ii. fig. 1, but has not its external mantle. It may be the ancestral form of it (both in an ontogenetic and phylogenetic sense).

Dimensions.—Main axis 0.11, equatorial axis 0.07; greatest breadth 0.08; pores 0.005, bars 0.005.

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

5. Cyphonium diattus, n. sp.

Cortical shell thin walled, with quite smooth surface; pores irregular, polygonal, mostly pentagonal or hexagonal, three to six times as broad as the bars; six to seven on the half meridian of the chamber, ten to twelve on its half equator. Medullary shells both spherical. (Resembles Cyphonium profundum, Ehrenberg, 1872, loc. cit., Taf. x. fig. 5, but does not possess the spines of the surface.)

Dimensions.—Main axis 0.13, equatorial axis 0.06; greatest breadth 0.08; pores 0.005 to 0.012, bars 0.002 to 0.004.

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

6. Cyphonium mammarium, n. sp.

Cortical shell thick walled, with smooth surface (sometimes a little rough); pores irregular, roundish, twice to three times as broad as the bars; eleven to twelve on the half meridian of each chamber, sixteen to nineteen on its half equator. Internal medullary shell spherical, external lenticular compressed, sometimes both spherical or both compressed. (Resembles the internal cortical twin-shell of Cyphocolpus virginis, Pl. 40, fig. 11.)

Dimensions.—Main axis 0.14, equatorial axis 0.08, greatest breadth 0.09; pores 0.004 to 0.006, bars 0.002.

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

Subgenus 2. Ommatocyrtis, Haeckel.

Definition.—Surface of the cortical shell thorny or spiny.

7. Cyphonium hexagonium, n. sp.

Cortical shell thin walled, with spiny surface; pores regular or subregular, hexagonal, twice to three times as broad as the bars; five to six on the half meridian, nine to ten on the half equator of each chamber. Radial spines between them conical, about as long as the pores. Medullary shells both spherical.

Dimensions.—Main axis 0.14, equatorial axis 0.08; greatest breadth of each chamber 0.1; pores 0.012, bars 0.004.

Habitat.—Pacific, central area, Station 268, depth 2900 fathoms.

8. Cyphonium facettarium, n. sp.

Cortical shell thick walled, with spiny surface; pores subregular, circular, with elevated hexagonal frames, twice as broad as the bars; eight to nine on the half meridian, fourteen to sixteen on the half equator of each chamber. In the corners of the hexagons (between every three meshes) arise radial spines, about twice as long as the pores. Both medullary shells spheroidal compressed. (This species is nearly identical with the internal cortical twin-shell of Peripanartus amphiconiscus, Pl. 40, fig. 5.)

Dimensions.—Main axis 0.12, equatorial axis 0.07; greatest breadth of both chambers 0.09; pores 0.01, bars 0.005, spines 0.02.

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

9. Cyphonium cribellum, n. sp. (Pl. 39, fig. 11).

Cortical shell thick walled, with spiny surface; pores regular, circular, about as broad as the bars; seven to eight on the half meridian of each chamber, thirteen to fifteen on its half equator. Radial spines between them conical, twice as long as the pores. Medullary shells both lenticular.

Dimensions.—Main axis 0.11, equatorial axis 0.06; greatest breadth 0.08; pores and bars 0.004.

Habitat.—North Atlantic, Station 353, surface.

10. Cyphonium profundum, Haeckel.

Cortical shell thin walled, with thorny surface; pores irregular, polygonal, three to six times as broad as the thin bars; five to six on the half meridian of each chamber, ten to twelve on its half equator. Thorns of the surface short. Medullary shells both spherical.

Dimensions.—Main axis 0.1, equatorial axis 0.06; greatest breadth 0.07; pores 0.005 to 0.012, bars 0.002, spines 0.005.

Habitat.—Pacific, tropical zone; Philippine Sea, depth 3300 fathoms, Ehrenberg; Stations 266 to 274, depth 2350 to 2925 fathoms.

11. Cyphonium ceratospyris, Haeckel.

Cortical shell thin walled, with spiny surface; pores irregular, roundish, three to nine times as broad as the bars; five to six on the half meridian of each chamber, eight to nine on its half equator. Spines of the surface partly very short, partly as long as the largest pores, either radially or obliquely inserted. Medullary shells both spherical. (Compare the detailed description and figures also of the soft body in my Monograph, loc. cit.)

Dimensions.—Main axis of the cortical shell 0.12, equatorial axis (in the stricture) 0.06; greatest breadth 0.08; pores 0.03 to 0.2, bars 0.002 to 0.006, spines 0.05 to 0.015.

Habitat.—Mediterranean (Messina), Canary Islands (Lanzerote), Haeckel.

Genus 157. Cypassis,^[196] n. gen.

Definition.—Cyphinida with double cortical shell and double medullary shell, without polar spines or tubes.

The genus Cypassis differs from Cyphonium by duplication of the cortical twin-shell; from the outer surface of the simple twin-shell arise numerous radial spines, which become connected by anastomosing transverse branches, and in this manner form an outer envelope or mantle. Cypassis may also be regarded as a Cromyodruppa, the double cortical shell of which is constricted in the equatorial plane.

Subgenus 1. Didymospyris, Haeckel (1881).

Definition.—Surface of the shell smooth, without thorns or spines.

1. Cypassis palliata, n. sp.

Inner cortical shell thin walled, with regular, circular, hexagonally-framed pores, twice as broad as the bars; seven to eight on the half meridian of each chamber, ten to twelve on its half equator. Outer cortical shell very thin, with smooth surface, and very small, irregular, roundish pores, twice to five times smaller than those of the inner shell. Distance between the two cortical shells equals the diameter of the outer medullary shell, which, like the inner, is spherical. (The network of this species resembles that of Peripanartus amphiconiscus, Pl. 40, fig. 5.)

Dimensions.—Main axis of the external cortical shell 0.18, of the internal 0.12; greatest breadth (in the equator of each chamber) of the former 0.13, of the latter 0.09; pores of the outer 0.002 to 0.005, of the inner shell 0.01, bars 0.002 to 0.005.

Habitat.—South Pacific, Station 288, surface.

2. Cypassis eucolpos, n. sp.

Inner cortical shell thick walled, with regular, circular pores, twice as broad as the bars (without hexagonal frames); nine to ten on the half meridian of each chamber, fifteen to seventeen on its half equator. Outer cortical shell very thin, with smooth surface, and very small, irregular, roundish pores, twice to three times smaller than those of the inner shell. Distance between the two cortical shells about one and a half times the diameter of the inner medullary shell, which, like the outer, is spherical. (The inner cortical shell resembles that of Cannartiscus amphiconiscus, Pl. 39, fig. 19, but without polar tubes.)

Dimensions.—Main axis of the external cortical shell 0.2, of the internal 0.15; greatest breadth of the former 0.16, of the latter 0.12; pores of the outer 0.002, of the inner 0.006, bars 0.003.

Habitat.—South Atlantic, Station 319, surface.

Subgenus 2. Didymocyrtis, Haeckel (1862).

Definition.—Surface of the cortical shell thorny or spiny.

3. Cypassis entomocora, Haeckel.

Inner cortical shell thick walled, with regular, circular pores, twice as broad as the bars (without hexagonal frames); eight to nine on the half meridian of each chamber, ten to eleven on its half equator. Outer cortical shell thin walled, with regular, circular pores like those of the inner. Distance between the two cortical shells equals about twice the diameter of one pore (or the short axis of the lenticular double medullary shell). Surface covered with short conical spines (in the figure of Ehrenberg broken off).

Dimensions.—Main axis of the external cortical shell 0.2, of the internal 0.15; greatest breadth of the former 0.13, of the latter 0.1; pores of the outer 0.005 to 0.01, of the inner 0.01, bars 0.004; length of the surface spines 0.005 to 0.01.

Habitat.—Fossil in the Tertiary rocks of Barbados, Bermuda, and Sicily (Caltanisetta); also living in the greatest depth of the Pacific, Stations 268, 225, depth 2900 to 4475.

4. Cypassis puella, n. sp. (Pl. 39, fig. 13).

Internal cortical shell thin walled, with irregular, circular pores of very different size, once to four times as broad as the bars; fourteen to fifteen on the half meridian of each chamber, eighteen to twenty on its half equator. Outer cortical shell thin walled, with irregular, circular pores, only one-third to one-half as large as those of the inner. Distance between the two shells equals the largest diameter of the double lenticular medullary shell. Surface of both cortical shells covered with short conical spines (not longer than the largest pores).

Dimensions.—Main axis of the external cortical shell 0.2, of the internal 0.15, of the central capsule 0.1; greatest breadth of the first 0.14, of the second 0.1, of the third 0.07; pores of the outer shell 0.001 to 0.005, of the inner 0.002 to 0.01, bars 0.002 to 0.003; length of the surface spines 0.005 to 0.01.

Habitat.—Pacific, central area; Stations 266 to 274, surface; Atlantic, Canary Islands (Haeckel), Station 354, surface.

5. Cypassis halicora, n. sp.

Internal cortical shell thin walled, with irregular, roundish pores, once to three times as broad as the bars; ten to eleven on half meridian of each chamber, fourteen to sixteen on its half equator. Outer cortical shell thin walled, with very delicate network, spindle-like, with conical prolongations at both poles. Distance between the two shells larger than the greatest diameter of the double lenticular medullary shell. Surface of both cortical shells covered with innumerable small thorns. (Resembles closely Cyphocolpus virginis, Pl. 40, fig. 11, but without the third shell.)

Dimensions.—Main axis of the external cortical shell 0.21, of the internal 0.14, greatest breadth of the former 0.13, of the later 0.09; pores 0.003 to 0.009; bars of the outer shell 0.001, of the inner 0.004.

Habitat.—Indian Ocean, Ceylon (Haeckel), surface.

Genus 158. Cyphocolpus,^[197] n. gen.

Definition.—Cyphinida with triple cortical shell and double medullary shell, without polar spines or tubes.

The genus Cyphocolpus differs from both foregoing genera by the increased number of the cortical twin-shells. Whilst these are simple in Cyphonium, double in Cypassis, they are triple in Cyphocolpus, composed of three concentric envelopes. The three genera named represent a phylogenetic series, which is repeated in the ontogenetic development of Cyphocolpus.

1. Cyphocolpus didymus, n. sp.

Inner cortical shell with circular, subregular pores, twice as broad as the bars; five to six on the half meridian of each chamber, eight to ten on its half equator. Middle cortical shell also with subregular, circular pores of the same size. Outer cortical shell with smooth surface, with more irregular, roundish pores of very different size. The distance between every two shells equals the diameter of the inner medullary shell, which, like the outer, is spheroidal.