Subfamily 1. Lithocyclida, Haeckel, 1881, Prodromus, p. 458

Definition.—Coccodiscida with simple circular disk, without any radial appendages of the margin (either solid radial spines or chambered arms).

Genus 196. Lithocyclia, Ehrenberg, 1847, Monatsber. d. k. preuss. Akad. d. Wiss. Berlin, p. 54.

Definition.—Coccodiscida with simple circular margin of the disk, without radial appendages. Medullary shell simple.

The genus Lithocyclia is the most simple form of Coccodiscida, and represents the common ancestral form of this family, from which all other genera of it can be derived. The lenticular, biconvex disk is quite simple, composed of a variable number of concentric, circular, chambered rings, which are pierced by radial beams, and which surround the circular lenticular cortical shell or "phacoid shell." The latter contains a simple spherical medullary shell in its centre, and is connected with it by radial beams. The margin of the disk is circular, quite simple, without radial spines or chambered arms.

1. Lithocyclia cingulata, n. sp.

Phacoid shell (or lenticular porous cortical shell) three times as broad as the spherical enclosed medullary shell, surrounded by one single chambered girdle or ring (with about forty chambers of equal size, separated by radial beams). Margin of the disk circular, smooth. Pores of the convex covering plates regular, circular; eight on the radius of the phacoid shell, two on the breadth of the ring.

Dimensions.—Diameter of the disk (with one ring) 0.13, of the phacoid shell 0.1, of the medullary shell 0.033.

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

2. Lithocyclia lenticula, n. sp. (Pl. , figs. 3, 4).

Phacoid shell two and a half times as broad as the enclosed medullary shell, surrounded by three chambered girdles of equal size, which are divided by piercing radial beams each into about fifty chambers. Margin of the disk thorny. Pores irregular, roundish; seven on the radius of the phacoid shell, two on the breadth of each girdle.

Dimensions.—Diameter of the disk (with three girdles) 0.2, of the phacoid shell 0.11, of the medullary shell 0.045.

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

3. Lithocyclia ocellus, Ehrenberg.

Lithocyclia ocellus, Ehrenberg, 1854, Mikrogeol., Taf. xxxvi. fig. 30; Abhandl. d. k. Akad. d. Wiss. Berlin, 1875, Taf. xxix. fig. 3.

Phacoid shell three times as broad as the medullary shell, surrounded by numerous (seven to eleven) chambered rings, which are divided by piercing radial beams each into sixty to ninety chambers. Margin of the disk smooth. Pores regular, circular; nine on the radius of the phacoid shell, one single pore on each chamber.

Dimensions.—Diameter of the disk (with eleven rings) 0.22, of the phacoid shell 0.1, of the medullary shell 0.035.

Habitat.—Fossil in the rocks of Barbados.

4. Lithocyclia monococcus, n. sp.

Stephanopyxis dubiosa (?), Bury, 1862, Polycystins of Barbados, pl. xiii. figs. 1, 2.

Phacoid shell four times as broad as the medullary shell, surrounded by numerous (five to eight) chambered rings, which are divided by piercing radial beams each into fifty to seventy chambers. Margin of the disk thickened, thorny. Pores regular, circular; seven on the radius of the phacoid shell, one single pore on each chamber.

Dimensions.—Diameter of the disk (with eight rings) 0.18, of the phacoid shell 0.12, of the medullary shell 0.03.

Habitat.—Pacific, central area, Station 267, depth 2700 fathoms; also fossil in the rocks of Barbados.

5. Lithocyclia heteropora, n. sp.

Phacoid shell two and a third times as broad as the medullary shell, surrounded by five to nine chambered rings, which are divided by piercing radial beams each into fifty to seventy chambers. Margin of the disk smooth. Pores very different in the inner and outer part of the surface; in the phacoid shell larger, regular, circular, eight on its radius, in the chambered periphery very small and irregular, somewhat spongy.

Dimensions.—Diameter of the disk (with nine rings) 0.2, of the phacoid shell 0.13, of the medullary shell 0.055.

Habitat.—Pacific, central area, Station 263, depth 2650 fathoms.

Genus 197. Coccodiscus, Haeckel, 1862, Monogr. d. Radiol., p. 485.

Definition.—Coccodiscida with simple circular margin of the disk, without radial appendages. Medullary shell double.

The genus Coccodiscus has quite the same form and structure as the preceding Lithocyclia, and differs from it only in the double medullary shell, composed of two concentric latticed spheres; sometimes the inner medullary shell is spherical, the outer lenticular; the latter is connected with the lenticular phacoid shell (or cortical shell) by radial beams.

1. Coccodiscus lamarckii, n. sp. (Pl. , fig. 1).

Phacoid shell (or lenticular porous cortical shell) very thick walled (as thick as one ring), three times as broad as the outer and seven times as broad as the inner medullary shell, surrounded by two to three chambered rings of equal breadth, each of which is divided by piercing radial beams into thirty-six to forty square chambers. Margin of the disk circular, smooth. Pores regular, circular, of equal size; ten on the radius of the phacoid shell, two on the breadth of each chamber.

Dimensions.—Diameter of the disk (with two rings) 0.2, of the phacoid shell 0.14, outer medullary shell 0.05, inner 0.02.

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

2. Coccodiscus darwinii, Haeckel.

Coccodiscus darwinii, Haeckel, 1862, Monogr. d. Radiol., p. 486, Taf. xxviii. figs. 11, 12.

Phacoid shell three times as broad as the outer and nine times as broad as the inner medullary shell, surrounded by five to eight chambered rings of equal breadth, each of which is divided by forty piercing radial beams into forty square chambers of equal size. Margin of the disk smooth, circular. Pores irregular, roundish, of unequal size; eleven on the radius of the phacoid shell, one to two on each chamber.

Dimensions.—Diameter of the disk (with eight rings) 0.32, of the phacoid shell 0.11, outer medullary shell 0.036, inner 0.012.

Habitat.—Mediterranean, Messina, surface.

3. Coccodiscus goethei, n. sp. (Pl. , fig. 2).

Phacoid shell two and a half times as broad as the outer and five times as broad as the inner medullary shell, surrounded by three to seven chambered rings of equal breadth, each of which is divided by piercing radial beams into sixty to eighty chambers. Margin of the disk thorny. Pores regular, circular; eight on the radius of the phacoid shell, a single one on the breadth of each chamber.

Dimensions.—Diameter of the disk (with seven rings) 0.25, of the phacoid shell 0.1, of the medullary shell 0.04, inner 0.02.

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