Page:Scientific results HMS Challenger vol 18 part 1.djvu/668

460 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.

Definition.— 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