Page:Scientific results HMS Challenger vol 18 part 1.djvu/631

Rh Dimensions.—Diameter of the disk 0.25, of the medullary shell 0.06, of the pores 0.002.

Habitat.—South Pacific, Station 288, surface.

4. Sethodiscus lenticula, n. sp. (Pl. 33, figs. 1, 2).

Disk with smooth surface, four times as broad as the medullary shell. Pores irregular, polygonal; eight to nine on the radius of the disk. (The pores of the medullary shell, fig. 2, are also irregular, polygonal, or roundish.)

Dimensions.—Diameter of the disk 0.17, of the medullary shell 0.04, of the pores 0.01.

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

5. Sethodiscus macrococcus, n. sp. (Pl. 33, fig. 3).

Disk with smooth surface, two and a half times as broad as the medullary shell. Pores irregular, polygonal; eleven to twelve on the radius of the disk. (The pores of the medullary shell, fig. 3, are regular, circular, with elevated hexagonal frames between them. The figured specimen is a young one, both halves of the biconvex disk being not yet united in the equatorial plane.)

Dimensions.—Diameter of the disk 0.16, of the medullary shell 0.065, of the pores 0.01.

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

6. Sethodiscus micrococcus, n. sp.

Disk with smooth surface, five times as broad as the medullary shell. Pores irregular, roundish, very small; twenty-six to twenty-eight on the radius of the disk. (The pores of the small medullary shell are regularly circular, of the same size as those of the disk.)

Dimensions.—Diameter of the disk 0.2, of the medullary shell 0.04, of the pores 0.002.

Habitat.—South Atlantic, Station 335, depth 1425 fathoms.

Definition.—Surface of the disk with elevated radial ribs or spines.

7. Sethodiscus radiatus, Haeckel.

Haliomma radians, Ehrenberg, 1854, Mikrogeol., Taf. xix. fig. 50.

Haliomma radiatum, Ehrenberg, 1854, Mikrogeol., Taf. xxi. fig. 54.

Disk with radiated surface, four times as broad as the medullary shell. Pores regularly circular; nine to ten on the radius of the disk, arranged in radial series (about forty), which are separated by smooth crests, not prominent on the smooth margin.

Dimensions.—Diameter of the disk 0.12, of the medullary shell 0.03, of the pores 0.003.

Habitat.—Fossil in Tertiary deposits of the Mediterranean, Greece, Sicily, Oran, &c.