Page:Scientific results HMS Challenger vol 18 part 1.djvu/459

Rh

Definition.—Radial main spines with three rows of lateral branches (one row on each edge).

3. Astrosphæra sideræa, n. sp.

Inner shell with regular, hexagonal meshes, six times as broad as the bars, and covered with numerous short bristle-shaped by-spines; outer shell four times as broad, with simple triangular meshes, and rows of long bristle-shaped by-spines arising from the bars. Radial main spines with three serrated edges and three rows of lateral branches (four branches on each edge).

Dimensions.—Diameter of the outer shell 0.6, inner 0.15.

Habitat.—Central Pacific, Station 266, surface.

4. Astrosphæra stellata, n. sp. (Pl. 19, fig. 5).

Diplosphæra stellata, Haeckel, 1881, Prodrom. et Atlas.

Inner shell with regular, hexagonal, six-rayed meshes, each bar being crossed by a transverse tangential rod, at each nodal-point a long bristle-shaped by-spine; outer shell three times as broad, with simple triangular meshes and denticulated thin bars, bearing a row of bristle-shaped radial by-spines. Radial main spines in the proximal half with three serrated edges, in the distal half with three rows of curved lateral branches (five branches on each edge).

Dimensions.—Diameter of the outer shell 0.6, inner 0.2.

Habitat.—Central Pacific, Station 274, surface.

Definition.— with three concentric, spherical, lattice-shells, united by radial beams.

Definition.— with three concentric lattice-spheres and numerous simple radial spines of one kind.

The genus Actinomma is here restricted to those which combine the possession of three concentric lattice-shells with numerous radial spines on the surface; the spines are all simple, being of one and the same kind. Commonly two of the three shells are intracapsular medullary shells, connected by radial beams (piercing