Page:Scientific results HMS Challenger vol 18 part 2.djvu/721

Rh branches, which are partly confluent and fenestrated (similarly as in Pl. 107, fig. 1), but not forming an outer lattice-shell. Meshes irregularly polygonal.

Dimensions.—Diameter of the shell 3.3, length of the spines 6 to 9, breadth 0.03.

Habitat.—Tropical Atlantic, Station 347, depth 2250 fathoms.

11. Orosphæra arborescens, n. sp. (Pl. 106, fig. 3).

Orothamnus arborescens, Haeckel, 1881, Atlas, loc. cit.

Radial spines cylindrical, rough, more or less curved, somewhat longer than the diameter of the subspherical or slightly ellipsoidal shell, and at the thicker base three times as broad as its smooth bars, bearing numerous irregularly branched and curved, sometimes confluent, lateral branches. Meshes irregularly quadrangular.

Dimensions.—Diameter of the shell 1.2 to 1.6, length of the spines 1.5 to 2.2, breadth 0.06.

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

Definition.— with a simple, polyhedral or subspherical lattice-shell, and with numerous pyramidal elevations on its surface, the top of which bears a radial spine.

The genus Oroscena differs from the preceding Orosphæra in the possession of numerous pyramidal or tent-shaped elevations, each of which bears on its top a radial spine. It exhibits therefore the same relation to the latter that Sagoscena does to Sagosphæra and Auloscena to Aulosphæra. The bases of the radial spines are usually connected by prominent concave crests, the edges of the pyramids. The species described of Oroscena seem to be very variable and transformistic.

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

1. Oroscena gegenbauri, n. sp. (Pl. 106, fig. 4).

Radial spines club-shaped, about half as long as the radius of the shell, cylindrical and finely sulcate in the basal third, ovate and elegantly dimpled in the distal two-thirds. The bases of the radial spines are connected by prominent concave crests, which form the edges of the polyhedral shell. Meshes irregularly polygonal, the majority quadrangular, separated by denticulate bars.