Page:Scientific results HMS Challenger vol 18 part 1.djvu/733

Rh Dimensions.—Radius of each arm (length from the centre to the distal end) 0.13; breadth of the truncated end 0.1.

Habitat.—Tropical Pacific, Philippine Sea, Station 200, depth 250 fathoms.

2. Dictyastrum bandaicum, Haeckel.

Rhopalastrum bandaicum, Harting, 1863, Mikr. Fauna Banda-Zee, p. 16, Taf. iii. fig. 45.

Arms nearly square, with convex edges, in the middle a little broader than at both ends, about half the diameter of the central disk. Differs from the nearly allied preceding species by the half size of the arms and the convex edges.

Dimensions.—Radius of each arm 0.12, its greatest breadth 0.07.

Habitat.—Tropical Pacific, Banda Sea, Harting.

3. Dictyastrum hexagonum, n. sp. (Pl. 43, fig. 7).

Rhopalastrum hexagonum, Haeckel, 1880, Atlas (pl. xliii. fig. 1).

Arms nearly triangular, one and a third times as broad at the distal end as long, and three times as broad as at the base. Central disk about the same diameter. In each arm six simple broad chambers. If we connect the six corners of the truncated distal ends by straight lines, we get a regular hexagon.

Dimensions.—Radius of each arm 0.17, basal breadth 0.06, terminal breadth 0.17.

Habitat.—Equatorial Atlantic, Station 347, surface.

4. Dictyastrum trirrhopalum, n. sp.

Arms club-shaped, five times as long as broad at the base, at the thickened end three times as broad as at the base. Diameter of the central disk equals half the length of the arms. (Similar to Rhopalastrum malleus, Pl. 43, fig. 1, but with three equal angles and much smaller disk.)

Dimensions.—Radius of each arm 0.25, basal breadth 0.04, distal breadth 0.12.

Habitat.—Pacific, central area, Station 273, surface.

Definition.—Arms on the distal end provided with terminal spines.

5. Dictyastrum trispinosum, n. sp. (Pl. 43, fig. 5).

Rhopalastrum trispinosum, Haeckel, 1881, Prodromus et Atlas (pl. xliii. fig. 5).

Arms trapezoid, at the rounded distal end twice as broad as at the base, with a strong and short, conical, terminal spine. Diameter of the circular central disk about equal to the length and the greatest breadth of the arms.

Dimensions.—Radius of each arm 0.15, basal breadth 0.06, distal breadth 0.11.

Habitat.—Equatorial Atlantic, Station 347, surface.