Chapter XI: Literature and History (17)

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.

_Ommatospyris lævis_, Ehrenberg, 1872, Monatsber. d. k. preuss. Akad. d.
Wiss. Berlin, p. 318.

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.)

{362}_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 {363}(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.

_Ommatospyris coscinoides_, Haeckel, 1881, Prodromus, p. 462.

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, 12_a_).

_Ommatospyris virginea_, Haeckel, 1881, Prodromus et Atlas (pl. xxxix.
fig. 12_a_).

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. 12_a_) 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.

_Ommatospyris ethmaria_, Haeckel, 1881, Prodromus, p. 462.

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.

{364}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.

_Didymocyrtis hexagonia_, Haeckel, 1881, Prodromus.

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 {365}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.

_Didymocyrtis facettaria_ Haeckel, 1881, Prodromus.

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.

_Ommatospyris profunda_, Ehrenberg, 1872, Abhandl. d. k. Akad. d. Wiss.
Berlin, p. 297, Taf. viii. fig. 5, Taf. x. fig. 5.

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.

{366}11. _Cyphonium ceratospyris_, Haeckel.

_Didymocyrtis ceratospyris_, Haeckel, 1862, Monogr. d. Radiol., p. 445,
pl. xxii. figs. 14-16.

_Haliomma didymocyrtis_, Haeckel, 1860, Monatsber. d. k. preuss. Akad. d.
Wiss. Berlin, p. 816.

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.

{367}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.

_Astromma entomocora_, Ehrenberg, 1847, Mikrogeol., Taf. xxii. fig. 32.

_Haliomma didymum_, Ehrenberg, 1844, Monatsber. d. k. preuss. Akad. d.
Wiss. Berlin, p. 83.

? _Haliomma amphisiphon_, Ehrenberg, 1844, Monatsber. d. k. Akad. d.
Wiss. Berlin, p. 267.

_Ommatospyris entomocora_, Ehrenberg, 1875, Abhandl. d. k. Akad. d. Wiss.
Berlin, pp. 66, 74.

? _Ommatocampe trinacria_, Stöhr, 1880, Palæontogr., vol. xxvi. p. 90,
Taf. ii. fig. 1.

_Didymospyris entomocora_, Haeckel, 1881, Prodromus.

_Didymocyrtis entomocora_, Haeckel, 1862, Monogr. d. Radiol., p. 445.

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).

_Didymospyris colpodes_, Haeckel, 1881, Prodromus et Atlas (pl. xxxix.,
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 {368}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.

{369}_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).

_Zygartus virginis_, Haeckel, 1881, Prodromus et Atlas (pl. xl. 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.

{370}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).

_Cyphinidium amphilophus_, Haeckel, 1882, Atlas (pl. xxxix. 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.

_Ommatospyris penicillata_, Ehrenberg, 1872, Monatsber. d. k. preuss.
Akad. d. Wiss. Berlin, p. 318; Abhandl. d. k. Akad. d. Wiss. Berlin, Taf.
viii. fig. 4.

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.

{371}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.

_Ommatospyris apicata_, Ehrenberg, 1872, Monatsber. d. k. preuss. Akad.
d. Wiss. Berlin, p. 317.

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).

{372}_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).

_Cannartidium amphiconiscus_, Haeckel, 1882, Atlas (pl. xxxix. 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; {373}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.)

{374}_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.

"Curious twin Polycystin," Bury, 1862, Polycystins of Barbados, pl. xx.
fig. 4.

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.

? _Haliomma amphisiphon_, Ehrenberg, 1844, Monatsber. d. k. preuss. Akad.
d. Wiss. Berlin, p. 267.

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. 18_a_).

_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.

{375}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.

{376}_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._

On both poles of the main { Cortical shell simple, 163. _Panartus_.
axis neither peculiar {
polar spines nor { Cortical shell double or
fenestrated tubes. { triple, 164. _Peripanartus_.

On both poles of the main { Cortical shell simple, 165. _Panicium_.
axis a large apical {
spine or a group of { Cortical shell double or
polar spines. { triple, 166. _Peripanicium_.

On both poles of the main { Cortical shell simple, 167. _Panarium_.
axis a conical or {
cylindrical fenestrated { Cortical shell double or
tube. { triple, 168. _Peripanarium_.

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.

{377}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 {378}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.

{379}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 {380}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.

_Ommatocampe profundissima_, Ehrenberg, 1872, Abhandl. d. k. Akad. d.
Wiss. Berlin, p. 297, Taf. viii. fig. 6.

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 {381}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.

_Ommatocampe setosa_, Ehrenberg, 1872, Abhandl. d. k. Akad. d. Wiss.
Berlin, p. 297, Taf. viii. fig. 7.

Both proximal chambers kidney-shaped, broader than the two hemispherical distal chambers. Meshes of the cortical shell irregular, polygonal, or subregular hexagonal; at the base of each {382}distal chamber a circle of large square meshes. The breadth of the pores is eight to twelve times that of the bars between them. The whole surface is covered with small bristle-like spines.

_Dimensions._--Total length of the cortical shell 0.14, greatest breadth (in the equator of each proximal chamber) 0.07; meshes 0.008 to 0.015, bars 0.002, spines 0.01.

_Habitat._--Pacific (Philippine and Californian Sea) 3300 and 2300 fathoms, Ehrenberg; Station 200, depth 250 fathoms; Station 253, depth 3125 fathoms.

15. _Panartus pluteus_, n. sp. (Pl. 40, fig. 2).

Both proximal chambers kidney-shaped, with irregular, roundish pores, twice to four times as broad as the bars; their surface everywhere covered with short conical thorns. From both polar circles arise ten to twelve radial rods, which bear a fenestrated cap, and form thus either the beginning of a second, external, cortical shell, or (if remaining thus) two imperfect distal chambers. The spherical segment, which forms their surface, is concentric with the proximal chambers, is perforated by the same irregular, roundish pores, and covered with numerous bristle-like spines.

_Dimensions._--Main axis of the cortical shell 0.17, equatorial axis (in the constriction) 0.06; distance between the proximal and distal chambers 0.03; pores 0.003 to 0.01, bars 0.003 to 0.005.

_Habitat._--Pacific, central area, Station 272, depth 2600 fathoms.

Genus 164. _Peripanartus_,[203] n. gen.

_Definition._--#Panartida# with double cortical shell and double medullary shell, without polar spines or tubes on both poles of the main axis.

The genus _Peripanartus_ differs from _Panartus_ only in the development of an outer reticulated envelop, which mantle-like surrounds the shell and represents a second or external cortical shell. This mantle or veil envelops either the whole internal cortical shell or only both proximal chambers. _Peripanartus_ exhibits the same relation to _Panartus_ as in the foregoing ancestral family _Cypassis_ bears to _Cyphonium_.

Subgenus 1. _Peripanartula_, Haeckel.

_Definition._--Surface of the outer cortical shell smooth, without spines or thorns.

1. _Peripanartus palliatus_, n. sp.

Internal cortical shell with four kidney-shaped chambers of equal size and similar form, identical with the cortical shell of _Panartus tetrathalamus_ and _Panartus quadrijugus_ (Pl. 40, fig. 3), with irregular, roundish pores, twice to three times as broad as the bars. It differs from these two species {383}only by the external cortical shell enveloping the whole internal one, in the same manner as in _Peripanartus cylindrus_ (Pl. 40, fig. 6). The two shells are connected by numerous radial rods. The surface of the outer cortical shell is quite smooth, its irregular, roundish pores about half as large as those of the inner cortical shell.

_Dimensions._--Main axis of the external cortical shell 0.27, of the internal 0.2; greatest breadth of the former (in the equator of each chamber) 0.13, of the latter 0.09; pores of the external cortical shell 0.002 to 0.004, of the internal 0.004 to 0.008; bars of the former 0.002, of the latter 0.003.

_Habitat._--Pacific, central area, Stations 271, 272, depth 2425 to 2600 fathoms.

2. _Peripanartus lævigatus_, n. sp.

Internal cortical shell with four unequal chambers, both proximal kidney-shaped (with subregular polygonal pores, twice to three times as broad as the bars), both distal nearly hemispherical, with subregular, roundish pores of half that size. External cortical shell envelops only the proximal chambers, and appears as the direct continuation of the internal shell of the distal chambers, with the same small roundish pores. The outer surface is quite smooth. This species has nearly the same structure as _Peripanicium amphicorona_ (Pl. 40, fig. 8), but differs from it by the absence of the polar spine-circles, and by the perfect smoothness of the surface.