Page:Scientific results HMS Challenger vol 18 part 1.djvu/633

Rh 2. Phacodiscus lentiformis, n. sp. (Pl. 35, fig. 8).

Disk with smooth surface, three and a half times as broad as the outer, and ten times as broad as the inner medullary shell. Pores regularly circular; twelve to thirteen on the radius of the disk. Margin of the disk sharp, as in a biconvex lens.

Dimensions.—Diameter of the disk 0.25, of the outer medullary shell 0.07, of the inner 0.025; pores 0.01.

Habitat.—Central Pacific, Station 265, depth 2900 fathoms; fossil in Barbados.

3. Phacodiscus grandis, n. sp.

Disk with thorny surface, five times as broad as the outer, and fifteen times as broad as the inner medullary shell. Pores regularly circular; twenty-two to twenty-four on the radius of the disk. Margin of the disk thick, rounded.

Dimensions.—Diameter of the disk 0.45, of the outer medullary shell 0.09, of the inner 0.03; pores 0.01.

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

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

4. Phacodiscus echiniscus, n. sp.

Disk with spiny surface, four times as broad as the outer, and ten times as broad as the inner medullary shell. Pores irregularly roundish; fourteen to fifteen on the radius of the disk. Margin of the disk sharp, as in a biconvex lens.

Dimensions.—Diameter of the disk 0.3, of the outer medullary shell 0.75, of the inner 0.03; pores 0.007.

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

5. Phacodiscus clypeus, n. sp. (Pl. 35, figs. 6, 9).

Disk with radiated surface, four times as broad as the outer, and twelve times as broad as the inner medullary shell. Pores regularly circular; sixteen to eighteen on the radius of the disk; in the distal half disposed in sixty to seventy radial series, which are separated by prominent crests; the sharp margin therefore a little jagged.

Dimensions.—Diameter of the disk 0.2, of the outer medullary shell 0.05, of the inner 0.017; pores 0.006.

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