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.
Genus 672. Orosphæra,[[290]] n. gen.
Definition.—Orosphærida 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.