Page:Scientific results HMS Challenger vol 18 part 1.djvu/780

572 arms. Chambered equatorial girdle with twenty to twenty-four subregular chambers (similar to Discopyle osculata, Pl. 48, fig. 19, but without any marginal osculum).

Dimensions.—Diameter of the disk 0.2, of the cortical shell 0.14, of the medullary shell 0.07.

Habitat.—Central Pacific, Station 265, depth 2900 fathoms.

2. Discozonium trigonium, n. sp.

Disk triangular, with thorny margin, four times as broad as the triangular, Triopyle-shaped medullary shell. Three gates of the cortical shell egg-shaped, scarcely as broad as the three arms. Chambered equatorial girdle with twenty-four to thirty irregular chambers.

Dimensions.—Diameter of the disk 0.24, of the cortical shell 0.2, of the medullary shell 0.06.

Habitat.—Central Pacific, Station 274, depth 2750 fathoms.

3. Discozonium hexagonium, n. sp. (Pl. 48, fig. 18).

Disk hexagonal, with spiny margin, four times as broad as the triangular, Triopyle-shaped medullary shell. Three gates of the cortical shell kidney-shaped, one and a half times as broad as the arms. Chambered equatorial girdle with twelve large regular chambers; the radial beams between them are prolonged into twelve strong pyramidal marginal spines (three perradial on the ends of the arms, three interradial on the radii of the gates, six adradial between the former and latter).

Dimensions.—Diameter of the disk 0.2, of the cortical shell 0.12, of the medullary shell 0.05.

Habitat.—Central Pacific, Station 271, depth 2425 fathoms.

Definition.— with Triopyle-shaped medullary shell and Pylodiscus-shaped cortical shell, which is surrounded by an equatorial chambered girdle. One peculiar osculum, surrounded by a corona of spines, on the margin of the disk.

The genus Discopyle differs from the preceding genus Discozonium in the development of a peculiar marginal osculum, and bears therefore to it the same relation as, in the Porodiscida, Ommatodiscus does to Porodiscus (compare above, p. 500). This peculiar osculum is here also surrounded by a corona of spines, and serves probably for the exit or outlet of a bunch of pseudopodia or a "sarcode-flagellum." Only two species of Discopyle have been observed, which represent perhaps better two different genera; in one species the disk is circular, in the other elliptical. In this latter the osculum lies on one pole of the main axis.