Page:Scientific results HMS Challenger vol 18 part 2.djvu/718

1594 1. Orona maxima, n. sp. (Pl. 107, fig. 5).

Shell spherical, with very irregular polygonal meshes. Bars of the loose network smooth or slightly spinulate, very thick, with a pinnulate axial canal.

Dimensions.—Diameter of the sphere 5.0 to 5.5, of the meshes 0.2 to 0.4, of the bars 0.01.

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

2. Orona robusta, n. sp.

Shell spherical, with irregular quadrangular meshes (intermingled with single triangular, pentagonal, and hexagonal meshes). Bars of the coarse network very thick, spinulate.

Dimensions.—Diameter of the sphere 3.0 to 3.6, of the meshes 0.05, of the bars 0.012.

Habitat.—Central Pacific, Station 268, depth 2900 fathoms.

3. Orona crassissima, n. sp. (Pl. 107, fig. 7).

Shell ellipsoidal, slightly prolonged in the main axis, with irregular polygonal meshes of very different sizes and unequal forms. Bars of the coarse network very thick, thorny and dimpled, their surface being covered with a network of prominent polygonal crests.

Dimensions.—Diameter of the sphere 3.0 to 4.0, of the meshes 0.2 to 0.5, of the bars 0.02 to 0.06.

Habitat.—South Pacific, Station 289, depth 2550 fathoms.

Definition.— with a simple, spherical (sometimes slightly ellipsoidal or polyhedral) lattice-shell without pyramidal elevations, but with numerous radial spines.

The genus Orosphæra differs from the preceding Orona, its ancestral form, in the development of simple or branched radial spines. It bears, therefore, the same relation to the latter that Acanthosphæra has to Cenosphæra. In the two latter genera, however, the bars of the network are solid, in the two former hollow. The species referred to Orosphæra are closely allied and require a further accurate examination.

Definition.—Radial spines simple, smooth or spiny, but neither branched nor arborescent.