Page:Scientific results HMS Challenger vol 18 part 2.djvu/732

1608 5. Sagosphæra coronilla, n. sp.

Radial spines slender, smooth, three to six arising from each nodal point of the network in divergent directions, about as long as its smooth bars, crowned at the distal end with a bunch of twenty to thirty radial terminal branches, and provided with a spinulate knob at the distal end (similar to Sagenoscena stellata, Pl. 108, fig. 3).

Dimensions.—Diameter of the sphere 3.0, length of the bars 0.1 to 0.2, breadth 0.002.

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

Definition.— with a delicate spherical shell, the thin wall of which is composed of a simple lattice-plate and covered with numerous pyramidal elevations; each pyramid bears on its top one or more radial spines, but has no axial rod in its radial axis.

The genus Sagoscena, and the following closely allied Sagenoscena (both very common and widely distributed), exhibit a peculiar and very remarkable structure of the delicate lattice-shell, similar to that which Auloscena represents among the Aulosphærida. The surface of the simple spherical lattice-shell is covered with numerous pyramidal or tent-shaped elevations. These elegant and delicate pyramids are, however, in Sagoscena usually not so regular as in the similar Auloscena; the edges of the pyramids are in the latter hollow cylindrical tubes, in the former thin solid threads. The top of each pyramid usually bears a bunch of apical spines.

1. Sagoscena castra, n. sp. (Pl. 108, fig. 1).

Pyramids subregular, of equal size and similar form, usually three-sided, crowned at the top with three divergent apical spines, which alternate with the three edges of the pyramids and bear a small spinulate terminal knob. (Some four-sided and single five-sided pyramids are often intermingled with the three-sided.)

Dimensions.—Diameter of the sphere 1.7 to 2.3, length of the bars 0.2 to 0.25, breadth 0.008.

Habitat.—South-Eastern Pacific, Stations 295, 296, surface.

2. Sagoscena tentorium, n. sp. (Pl. 108, fig. 6).

Pyramids subregular, of equal size and similar form, usually four-sided, crowned at the top with three divergent apical spines, which are trifurcate at the distal end. (Some three-sided and five-sided pyramids are often intermingled with the four-sided.)

Dimensions.—Diameter of the sphere 2.2, length of the bars 0.2 to 0.25, breadth 0.005.

Habitat.—South Pacific, Station 291, surface.