Dimensions.—Main axis of the outer cortical shell 0.3, of the middle 0.22, of the inner 0.15; greatest breadth of the inner cortical shell 0.1, its pores 0.01, bars 0.005.

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

2. Cyphocolpus virginis, n. sp. (Pl. 40, fig. 11).

Inner cortical shell with irregular, roundish pores, twice to three times as broad as the bars; eleven to twelve on the half meridian of each chamber, sixteen to eighteen on its half equator. Middle cortical shell with very delicate network, its irregular, polygonal pores of the same size as those of the inner, but separated by extremely thin bars. Outer cortical shell with spiny surface, and with more irregular, roundish pores of different size. The distance between each two shells is variable, and attains more than the diameter of the outer medullary shell, which, like the inner, is spheroidal, slightly compressed.

Dimensions.—Main axis of the outer cortical shell 0.26, of the middle 0.22, of the inner 0.14; greatest breadth of the inner cortical shell 0.09, its pores 0.004 to 0.006, bars 0.002.

Habitat.—Pacific, central area, Station 271, surface.

Genus 159. Cyphinus,^[198] Haeckel, 1881, Prodromus, p. 463.

Definition.—Cyphinida with simple cortical shell and simple medullary shell, with two opposite polar spines (or bunches of polar spines) on the poles of the main axis.

The genus Cyphinus differs from Cyphanta by the development of two opposite spines (or bunches of spines) on both poles of the main axis. It simulates therefore the bipolar formation of Stylartus, and differs from this in the possession of a medullary shell.

Subgenus 1. Cyphinoma, Haeckel.

Definition.—On both poles of the main axis only one single large spine.

1. Cyphinus amphacanthus, n. sp.

Cortical shell with smooth surface, and circular, regular pores, twice as broad as the bars; five to six pores on the half meridian of each chamber, ten to twelve on its half equator. On both poles of the main axis, one single, very strong, conical spine, about half as long as this axis, and half as broad at the base as the spherical medullary shell.

Dimensions.—Main axis of the cortical shell (without spines) 0.2, greatest breadth (in the equator of each chamber) 0.1; pores 0.006, bars 0.003; length of the polar spines 0.1, basal thickness of them 0.02.

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

2. Cyphinus dixiphus, n. sp.

Cortical shell with rough surface, and irregular, roundish pores, twice to four times as broad as the bars; eight to nine pores on the half meridian of each chamber, twelve to fourteen on its half equator. On both poles of the main axis, one single, strong, conical spine, with prominent edges at the base, and nearly as broad as the spherical medullary shell, nearly as long as the main axis.

Dimensions.—Main axis (without spines) 0.18, greatest breadth 0.13; pores 0.003 to 0.008, bars 0.002; length of the polar spines 0.16, basal thickness 0.03.

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

Subgenus 2. Cyphinura, Haeckel.

Definition.—On both poles of the main axis a bunch or circle of several spines.

3. Cyphinus amphilophus, n. sp. (Pl. 39, fig. 14).

Cortical shell thick walled, with rough surface, and subregular, circular pores of different size, twice to five times as broad as the bars; nine to ten pores on the half meridian of each chamber, twelve to fourteen on its half equator. On both poles of the main axis a bunch of six to eight strong conical spines, the largest of which are about as long as the greatest breadth of the shell; their basal part is furrowed, and nearly half as thick as the spherical medullary shell.

Dimensions.—Main axis of the cortical shell (without spines) 0.18 to 0.2, greatest breadth 0.1 to 0.12; pores 0.004 to 0.01, bars 0.002; length of the polar spines 0.04 to 0.12, basal thickness 0.02 to 0.04.

Habitat.—Pacific, central area, Station 271, depth 2425 fathoms.

4. Cyphinus penicillatus, Haeckel.

Cortical shell thin walled, with rough surface, and irregular, polygonal pores, six to eight times as broad as the bars; five to six pores on the half meridian of each chamber, nine to ten on its half equator. Around both poles of the main axis a polar circle of eight to ten divergent radial spines, scarcely thicker than the bars, and about as long as the diameter of the spherical medullary shell. (In the figure of Ehrenberg the network is too thin and the spines too short.)

Dimensions.—Main axis (without spines) 0.1, greatest breadth 0.09; pores 0.008 to 0.014, bars 0.001 to 0.002; length of the spines 0.02 to 0.04.

Habitat.—Pacific, Philippine Sea, 3300 fathoms, Ehrenberg; Station 206, depth 2100 fathoms.

Genus 160. Cyphinidium,^[199] n. gen.

Definition.—Cyphinida with simple cortical shell and double medullary shell, with two opposite polar spines (or bunches of polar spines) on the poles of the main axis.

The genus Cyphinidium differs from Cyphinus only in the duplication of the medullary shell, which is composed of two concentric spheres or somewhat compressed lenticular spheroids. It exhibits therefore the same relation to Cyphinus that Stylatractus in the Druppulida bears to Lithatractus. Possibly the two former genera are derived from the two latter by an annular constriction in the equatorial plane.

Subgenus 1. Cyphinidoma, Haeckel.

Definition.—On both poles of the cortical shell one single polar spine or a bunch of polar spines.

1. Cyphinidium amphistylium, n. sp.

Cortical shell thick walled, with smooth surface, and subregular, circular pores, twice to three times as broad as the bars; eight to ten on the half meridian, sixteen to eighteen on the half equator of each chamber. Both medullary shells spherical. The cortical shell resembles very much that of Cannartiscus amphiconiscus (Pl. 39, fig. 19), but exhibits instead of the hollow polar tubes two strong solid polar spines of conical form, half as long as the main axis, and as broad at the base as the inner medullary shell.

Dimensions.—Main axis of the cortical shell (without polar spines) 0.14, greatest breadth 0.1; pores 0.008, bars 0.004; length of the polar spines 0.08, basal thickness 0.02.

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

2. Cyphinidium apicatum, Haeckel.

Cortical shell thin walled, with thorny surface, and irregular, polygonal pores, three to five times as broad as the thin bars; eight to nine on the half meridian, thirteen to fifteen on the half equator of each chamber. On both poles a bunch of four to eight strong conical spines, the central of which (in the main axis) is much larger than the others, and twice as long as the diameter of the outer spheroidal medullary shell; size and number of the polar spines is very variable (commonly five to six).

Dimensions.—Main axis (without spines) 0.12, greatest breadth 0.08; pores 0.005 to 0.01, bars 0.002; length of the polar spines 0.02 to 0.06, basal thickness 0.01.

Habitat.—Northern Pacific, Californian Sea, depth 2500 fathoms, Ehrenberg; Station 253, depth 3125 fathoms.

Subgenus 2. Cyphinidura, Haeckel.

Definition.—On both poles of the cortical shell, a circle of divergent polar spines.

3. Cyphinidium coronatum, n. sp.

Cortical shell with thorny surface, and irregular, roundish pores, twice to four times as broad as the bars; seven to eight on the half meridian, eleven to thirteen on the half equator of each chamber. Around both poles of the main axis occurs a circle of ten to twelve strong, radially divergent spines, about as long as the diameter of the outer medullary shell, which, like the inner, is spheroidal. (This species is identical with the younger developmental stage of Panicium coronatum, Pl. 40, fig. 4, before the formation of two distal chambers.)

Dimensions.—Main axis 0.12, greatest breadth 0.1; pores 0.008 to 0.016, bars 0.004; length of the polar spines 0.02, thickness 0.005.

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

Genus 161. Cannartiscus,^[200] n. gen.

Definition.—Cyphinida with simple cortical shell and simple medullary shell, with two hollow fenestrated polar tubes, opposite on both poles of the main axis.

The genus Cannartiscus differs from Cyphanta in the development of two hollow fenestrated tubes, opposite on both poles of the main axis. It simulates therefore the characteristic formation of Cannartus, and differs from this Artiscid in the possession of a medullary shell.

1. Cannartiscus amphiconiscus, n. sp. (Pl. 39, fig. 19).

Cortical shell thick walled, smooth, with regular, circular pores, twice as broad as the bars; nine to ten on the half meridian, sixteen to eighteen on the half equator of each chamber. Polar tubes conical, about as long as one single chamber, on the base somewhat broader than the simple spherical medullary shell. Pores of the tubes only one-third as great as those of the chambers.

Dimensions.—Main axis of the cortical shell (without tubes) 0.14, greatest breadth 0.1; pores 0.008, bars 0.004. Length of the polar tubes 0.07, basal breadth 0.04; pores 0.003, bars 0.002.

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

2. Cannartiscus amphicylindrus, n. sp.

Cortical shell thick walled, rough, with subregular, circular pores, twice to four times as broad as the bars; six to seven on the half meridian, ten to twelve on the half equator of each chamber. Polar tubes cylindrical, on the distal end open (broken off?) nearly as long as the main axis, somewhat narrower than the spherical medullary shell. Pores of the tubes much smaller than those of the chambers.

Dimensions.—Main axis (without tubes) 0.17, greatest breadth 0.12; pores 0.006 to 0.012, bars 0.003. Length of the polar tubes 0.15, breadth of them 0.03; pores 0.003, bars 0.002.

Habitat.—Pacific, central area, Station 268, 2900 fathoms; the same form occurs fossil in the rocks of Barbados.

Genus 162. Cannartidium,^[201] n. gen.

Definition.—Cyphinida with simple cortical shell and double medullary shell, with two hollow fenestrated polar tubes, opposite on both poles of the main axis.

The genus Cannartidium differs from Cannartiscus and Cannartus in the duplication of the medullary shell, which is composed of two concentric spheres or compressed lenticular spheroids. The three genera named form therefore one morphological series, with identical cortical shell, and only differing in the absence or presence of a simple or double medullary shell.

Subgenus 1. Cannartidella, Haeckel.

Definition.—Surface of the cortical shell smooth or a little rough, but without spines or fenestrated protuberances.

1. Cannartidium amphiconicum, n. sp.

Cortical shell thick walled, smooth with regular circular pores twice as broad as the bars; eight to nine on the half meridian, fifteen to sixteen on the half equator of each chamber. Polar tubes conical, with smaller pores, tapering towards the closed apex, about as long as one single chamber, at the base one-third as broad as the equatorial constriction. Both concentric medullary shells spherical. (Nearly identical with Cannartiscus amphiconiscus, Pl. 39, fig. 19, but differs in the possession of the double medullary shell.)

Dimensions.—Main axis of the cortical shell (without tubes) 0.15, greatest breadth 0.11; pores 0.009, bars 0.004; length of the polar tubes 0.08, basal breadth 0.04.

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

2. Cannartidium amphicanna, Haeckel.

Cortical shell thick walled, rough, with regular, circular pores, not broader than the bars; six to seven on the half meridian, ten to twelve on the half equator of each chamber. Polar tubes cylindrical, at the distal end open (broken off?), nearly as long as the main axis, about one-third as broad as the equatorial constriction. Both concentric medullary shells spherical.

Dimensions.—Main axis 0.14, greatest breadth 0.11; pores and bars 0.005; length of the polar tubes 0.13, breadth of them 0.03.

Habitat.—Fossil in the Barbados deposits.

3. Cannartidium amphisiphon, Haeckel.

Cortical shell thick walled, rough, with irregular, roundish pores, twice to five times as broad as the bars; five to six on the half meridian, nine to ten on the half equator of each chamber. Polar tubes conical, with smaller pores, about as long as one single chamber, half as broad at the base as the equatorial constriction. (This deep-sea form is probably identical with that fossil species which Ehrenberg, in 1844, described as Haliomma amphisiphon, and which he afterwards, in 1875, erroneously identified with his Astromma entomocora (= Cypassis entomocora). But the figure given of the latter is quite different from the given diagnosis of the former.)

Dimensions.—Main axis of the cortical shell (without tubes) 0.13, greatest breadth 0.1; pores 0.006 to 0.12, bars 0.003; length of the polar tubes 0.07, basal breadth of them 0.04.

Habitat.—Tropical Atlantic, Antilles, Station 24, depth 390 fathoms; fossil in the Tertiary rocks of Bermuda.

4. Cannartidium bicinctum, n. sp. (Pl. 39, fig. 18).

Cortical shell thick walled, with a thickened ring-shaped protuberance in the greatest breadth of both chambers. Pores subregular, circular, twice to three times as broad as the bars; seven to eight on the half meridian, thirteen to fifteen on the half equator of each chamber. Polar tubes conical, with smaller pores, somewhat shorter than the greatest breath, nearly as thick at the base as the outer spheroidal medullary shell (fig. 18a).

Dimensions.—Main axis (without tubes) 0.12, greatest breadth 0.08; pores 0.003 to 0.006, bars 0.002; length of the polar tubes 0.08, basal thickness 0.03.

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

Subgenus 2. Cannartidissa, Haeckel.

Definition.—Surface of the cortical shell with conical fenestrated protuberances in the greatest breadth of both chambers.

5. Cannartidium mammiferum, n. sp. (Pl. 39, fig. 16).

Cortical shell-thin walled, having a circle of six to eight conical protuberances in the greatest breadth of both chambers, each of which exhibits a central apical pore, surrounded by a circle of six to eight oblique larger pores. Between the protuberances occur nine to ten pores on the half meridian of each chamber, circular, subregular, twice to three times as broad as the bars. Polar tubes cylindrical, conical at the closed end, with smaller pores, about as long as the greatest breadth of the chambers, as broad as the spherical outer medullary shell.

Dimensions.—Main axis (without tubes) 0.13, greatest breadth (including the protuberances) 0.1; pores 0.005 to 0.008, bars 0.003; length of the polar tubes 0.09, basal thickness 0.02.

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

6. Cannartidium mastophorum, n. sp. (Pl. 39, fig. 17).

Cortical shell thin walled, of the same form and structure as in the foregoing species, differs from this mainly in the form of the polar tubes, which are not cylindrical but conical, tapering gradually from the base towards the closed apex. Besides this, the conical protuberances (six in the greatest periphery of each chamber) are more regular and acute, with smaller and more numerous pores. Both medullary shells are here also spherical.

Dimensions.—Main axis (without tubes) 0.14, greatest breadth (including the protuberances) 0.13; pores 0.006 to 0.009, bars 0.004; length of the polar tubes 0.07, basal thickness 0.03.

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

Family XVI. Panartida, Haeckel (Pl. 40, figs. 1-9).

Definition.—Prunoidea with a four-jointed cortical shell, the external shell being divided by three parallel transverse constrictions into four chambers, in the centre enclosing two internal concentric shells (medullary shells). Central capsule cylindrical, commonly four-jointed (with three transverse annular constrictions).

The family Panartida (Pl. 40, figs. 1-9) is characterised by its four-jointed cortical shell, constantly composed of four chambers, lying one behind another in the elongated main axis. They are separated by three ring-like constrictions lying in three parallel transverse planes; the middle of these is the equatorial plane. In the centre of this latter lies constantly a double medullary shell.

The Panartida must be derived from the Cyphinida by further increase in the longitudinal or main axis, and by repetition of the equatorial constriction in two transverse planes parallel to it and at an equal distance from it.

The Medullary Shell is always double in this family, composed of two small concentric shells lying in the middle of the central capsule. They are either spherical or lenticular, compressed towards both poles of the main axis; sometimes the inner is spherical, the outer lenticular. From the equatorial circumference of the latter starts a number of radial beams, which perforate the central capsule, and are inserted into the equatorial constriction of the cortical shell. Commonly all radial beams lie in the equatorial plane, sometimes also a part of them on both sides of it.

The Cortical Shell is constantly composed of four completely latticed chambers, which are only separated by the three annular constrictions. In many species all four chambers have the same form and size (Pl. 40, fig. 3), but in the greater number of species both proximal (or central) chambers are different in size, shape, or structure from both distal (or polar) chambers. The cortical shell is either simple or double, composed of two concentric four-jointed shells; rarely it is triple or multiple, composed of three or more shells fitting one inside the other. Very often the outer cortical shell is incomplete, and only developed around the two proximal chambers of the complete inner cortical shell, both distal chambers of the latter remaining simple.

On both poles of the main axis often are developed solid spines (Panicium, Pl. 40, fig. 4) or hollow fenestrated tubes (Panarium, Pl. 40, fig. 9), as in the foregoing families. Besides this, the surface of the cortical shell may be armed with spines.

The Central Capsule of the Panartida is always cylindrical, on both poles hemispherical; commonly it is more or less distinctly four-jointed, with three ring-like constrictions corresponding to those of the enclosing cortical shell. From the inner surface of the latter it is separated by a thinner or thicker jelly-mantle.

Synopsis of the Genera of Panartida.

Genus 163. Panartus,^[202] n. gen.

Definition.—Panartida with simple cortical shell and double medullary shell, without polar spines or tubes on both poles of the main axis.

The genus Panartus represents the common ancestral form of all Panartida, as all other genera of this subfamily must be derived from it and are only further developmental stages, from an ontogenetic as well as from a phylogenetic point of view. The cortical shell of Panartus is constantly composed of four fenestrated chambers jointed to one another in the main axis; both proximal chambers are separated from one another by the equatorial ring-like constriction, in the centre of which lies the double medullary shell; both distal chambers are separated from the former by two other annular constrictions (in planes parallel to the equatorial plane). All four chambers may exhibit the same (kidney-shaped) form and structure (in the subgenera Panartella and Panartoma); or the proximal chamber may differ more or less in shape and size from the distal (in the subgenera Panartissa and Panartura). The outer surface of the cortical shell is sometimes smooth (as in Panartella and Panartissa), at other times spiny or thorny (as in Panartoma and Panartura). The double medullary shell is sometimes spherical, or commonly compressed at both poles and spheroidal or lenticular.

Subgenus 1. Panartella, Haeckel.

Definition.—Surface of the cortical shell smooth, without spines or thorns. All its four chambers exhibit nearly the same form and structure.

1. Panartus tetraplus, n. sp.

All four chambers of the cortical shell of the same form, size, and structure, kidney-shaped, twice as broad as long. Pores rather regular, hexagonal, all nearly of the same size and form, four times as broad as the thin bars; five to six pores on the half meridian, nine to ten on the half equator of each chamber. Surface of the cortical shell smooth, its main axis three times as long as its equatorial axis (in the median constriction). Both concentric medullary shells spherical; the equatorial axis of the outer half as long as that of the cortical shell. (All four chambers of this species have the same appearance as the two proximal chambers of Panartus diploconus, Pl. 40, fig. 1.)

Dimensions.—Main axis of the cortical shell 0.21, equatorial axis 0.07; breadth of every chamber 0.09; meshes 0.013, bars 0.03.

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

2. Panartus tetracolus, n. sp.

All four chambers of the cortical shell of the same form, size, and structure, kidney-shaped, twice as broad as long. Pores regular, circular, with hexagonal frame, twice as broad as the bars; six to seven pores on the half meridian, ten to twelve on the half equator of each chamber. Surface of the cortical shell smooth; its main axis three times as long as the equatorial axis. Both concentric medullary shells spheroidal, somewhat compressed at both poles; the equatorial axis of the outer almost equals half that of the cortical shell. (All four chambers of this species exhibit the structure of the two proximal chambers of Peripanartus amphiconus, Pl. 40, fig. 5.)

Dimensions.—Main axis of the cortical shell 0.24, equatorial axis 0.08; breadth of every chamber 0.01; meshes 0.01, bars 0.005.

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

3. Panartus tetrameres, n. sp.

All four chambers of the cortical shell of the same form, size, and structure, kidney-shaped, twice as broad as long. Pores rather regular, circular, without hexagonal frame, about as broad as the bars; five to six pores on the half meridian, ten to twelve on the half equator of each chamber. Surface of the cortical shell smooth, its main axis three times as long as the equatorial axis. Both concentric medullary shells spheroidal, compressed; the outer half as broad as the constriction. (This species is very much like Ommatocampe increscens, Stöhr, 1880, loc. cit., Taf. ii. fig. 2, and may be considered as the ancestral form of it.)

Dimensions.—Main axis of the cortical shell 0.2, equatorial axis 0.065; breadth of every chamber 0.08; meshes and bars 0.005.

Habitat.—Fossil in the Tertiary rocks of Sicily, Caltanisetta, Haeckel.

4. Panartus tetraphalangus, n. sp.

All four chambers of the cortical shell of the same form, size, and structure, kidney-shaped, twice as broad as long. Pores irregular, polygonal (mostly pentagonal or hexagonal), four to eight times as broad as the thin bars; four to seven on the half meridian, eight to fifteen on the half equator of each chamber. Surface of the cortical shell smooth, its main axis three times as long as its equatorial axis. Both concentric medullary shells compressed, the outer, half as broad as the constriction.

Dimensions.—Main axis of the cortical shell 0.26, equatorial axis 0.09; breadth of every chamber 0.12; meshes 0.003 to 0.02, bars 0.001 to 0.003.

Habitat.—Fossil in the rocks of Barbados, Haeckel.

5. Panartus tetrathalamus, n. sp. (Pl. 40, fig. 3).

All four chambers of the cortical shell of the same form, size, and structure, kidney-shaped, twice as broad as long. Pores irregular, roundish, twice to three times as broad as the bars; a circle of larger pores at the base of both distal chambers; five to six pores on the half meridian, ten to twelve on the half equator of each chamber. Surface of the cortical shell smooth; its main axis two and a half times as long as the equatorial axis. Both medullary shells spheroidal, compressed, the outer one-third as broad as the constriction. (In the specimen figured spines begin to arise from both distal chambers; this forms a transition to Panartus quadrijugus.)

Dimensions.—Main axis of the cortical shell 0.18, equatorial axis 0.07; breadth of every chamber 0.09; meshes 0.003 to 0.01, bars 0.002 to 0.004.

Habitat.—Cosmopolitan; Mediterranean, Atlantic, Pacific, in various depths.

Subgenus 2. Panartissa.

Definition.—Surface of the cortical shell smooth, without spines or thorns. Both its proximal chambers differ in form and structure from the two distal chambers.

6. Panartus diploconus, n. sp. (Pl. 40, fig. 1).

Both proximal chambers nearly ellipsoidal, one and a half times as broad as long, with regular hexagonal pores, four times as broad as the bars; five to six pores on the half meridian, nine to ten on the half equator of each chamber. Both distal chambers conical, with a circle of ten to twelve large square pores at the base; the other pores very small and numerous, roundish, sixteen to twenty in the height of each cone, and the same number on the half periphery of its base. Both concentric medullary shells compressed, the outer, half as broad as the constriction of the cortical shell, the surface of which is quite smooth.

Dimensions.—Total length of the shell (or main axis) 0.34; greatest breadth of each chamber 0.09; pores of the proximal chambers 0.013, bars 0.003; pores and bars of the distal chambers 0.003; large basal square pores 0.02.

Habitat.—Pacific, central area, Station 272, depth 2600 fathoms.

7. Panartus amphiconus, n. sp.

Both proximal chambers nearly kidney-shaped, one and a half times as broad as long, with regular, circular pores, with hexagonal frames, twice as broad as the bars; six to seven pores on the half meridian, ten to twelve on the half equator of each chamber. Both distal chambers conical, with a circle of ten to twelve very large pores at the base; the other pores very small, roundish, ten to fifteen in the height of each cone, twenty to thirty on the half basal periphery. Both concentric medullary shells compressed, the outer one-third as broad as the constriction of the cortical shell, whose surface is smooth. (This species resembles Peripanartus amphiconus, Pl. 40, fig. 5, but is without the surface spines and the outer envelope.)

Dimensions.—Total length of the shell 0.28; greatest breadth of the proximal chambers 0.1, of the distal chambers 0.14; pores of the former 0.008, of the latter 0.004; bars of both 0.003 to 0.005.

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

8. Panartus fusiformis, n. sp.

Both proximal chambers nearly ellipsoidal, one and a half times as long as broad, with irregular, roundish pores, twice to three times as broad as the bars; eight to ten pores on the half meridian, twelve to fifteen on the half equator of each chamber. Both distal chambers hemiellipsoidal or egg-shaped, somewhat higher and narrower than the proximal chambers, with a circle of larger square pores at their base; the other pores roundish and very irregular. Both medullary shells spheroidal, one-third as broad as the constriction of the cortical shell, whose surface is quite smooth. (This species is similar to Peripanartus atractus, Pl. 40, fig. 7, but is without the superficial spines and the equatorial girdle-like envelope of the latter.)

Dimensions.—Total length of the shell 0.25 to 0.3; greatest breadth (in the equator of the proximal chambers) 0.08 to 0.1; pores of the proximal chambers 0.008 to 0.012, pores of the distal chambers half their size, bars 0.002 to 0.006.

Habitat.—North Pacific, Station 237, surface.

9. Panartus profundissimus, Haeckel.

Both proximal chambers nearly ellipsoidal, with irregular, polygonal pores, six to eight times as broad as the bars; four to five pores on the half meridian, eight to nine on the half equator of each chamber. Both distal chambers hemispherical, with a very delicate irregular network. Medullary shells spherical; surface of the shell smooth.

Dimensions.—Total length of the shell 0.15; greatest breadth in the equator of the proximal chambers 0.08; pores of the proximal chambers 0.015, bars 0.002.

Habitat.—Philippine Sea, depth 3300 fathoms, Ehrenberg; Station 213, depth 2050 fathoms.

Subgenus 3. Panartoma, Haeckel.

Definition.—Surface of the cortical shell thorny, covered with scattered spines. All its four chambers exhibit the same form and structure.

10. Panartus quadriceps, n. sp.

All four chambers of the cortical shell of the same form, size, and structure, kidney-shaped, twice as broad as long. Pores rather regular, circular, with hexagonal frames, twice to three times as broad as the bars; six to seven pores on the half meridian, ten to twelve on the half equator of each chamber. Surface spiny; from the corners of the hexagonal frames (between every three pores) arise short radial spines. Both medullary shells spherical, the outer one-third as broad as the constriction of the cortical shell. (All the four chambers of this species have the same form as the two proximal chambers of Peripanartus amphiconus, Pl. 40, fig. 5.)

Dimensions.—Main axis of the cortical shell 0.24, equatorial axis 0.08; meshes 0.01, bars 0.003 to 0.005; length of the spines 0.01 to 0.02.

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

11. Panartus quadrijugus, n. sp.

All four chambers of the cortical shell of the same form and size, kidney-shaped, twice as broad as long. Pores irregular, roundish, twice to three times as broad as the bars; a circle of larger pores at the base of both distal chambers; six to eight pores on the half meridian, twelve to fourteen on the half equator of each chamber. Surface spiny, everywhere covered with small irregular thorns. (This species differs from the smooth Panartus tetrathalamus, Pl. 40, fig. 3, almost entirely by the thorny surface.)

Dimensions.—Main axis 0.2, equatorial axis 0.08; breadth of every chamber 0.1; meshes 0.005 to 0.01, bars 0.003, spines 0.01 to 0.02.

Habitat.—Cosmopolitan; on the surface of the Atlantic, Indian, and Pacific Oceans.

12. Panartus quadrigeminus, n. sp.

All four chambers of the cortical shell nearly of the same size and form, kidney-shaped, twice as broad as long. Pores irregular, polygonal (mostly pentagonal or hexagonal), six to eight times as broad as the thin bars; five to seven on the half meridian, twelve to sixteen on the half equator of each chamber. Surface of the cortical shell spiny, covered with numerous irregularly scattered, often oblique, bristle-like thorns.

Dimensions.—Main axis 0.27, equatorial axis 0.1; breadth of each chamber 0.13; meshes 0.01 to 0.02, bars 0.001 to 0.005.

Habitat.—Cosmopolitan; surface of the Atlantic and Pacific, many Stations.

Subgenus 4. Panartura, Haeckel.

Definition.—Surface of the cortical shell thorny, covered with scattered spines. Both its proximal chambers differ in form or structure from the two distal chambers.

13. Panartus spinosus, n. sp.

Both proximal chambers nearly ellipsoidal, with regular, circular pores enclosed by hexagonal frames. Both distal chambers conical, with a circle of ten to twelve large square pores at the base; the other pores small, roundish. The cortical shell of this species is quite the same as that of Panartus amphiconus (Pl. 40, fig. 5), but differs in the absence of the external envelope (or the second cortical shell), and is covered with short, conical spines on the whole surface.

Dimensions.—Total length of the cortical shell 0.25, greatest breadth (on the base of the distal chambers) 0.12; meshes of the proximal chambers 0.008, of the distal chambers 0.004; bars 0.002 to 0.04, spines 0.01 to 0.02.

Habitat.—North Pacific, Station 240, surface.

14. Panartus setosus, Haeckel.