Page:Scientific results HMS Challenger vol 18 part 1.djvu/795

Rh 5. Spongotrochus parma, n. sp.

Spongy framework of the disk in the inner part with five to eight spiral convolutions (or partly concentric rings), in the outer part quite irregular. Thirty to forty long, bristle-shaped, radial spines, about as long as the diameter of the disk, disposed on both flat sides of the disk, but not on the margin.

Dimensions.—Diameter of the disk 0.16; length of the radial spines 0.18, basal breadth 0.003.

Habitat.—South Atlantic, Station 325, surface.

Definition.— with two or more (commonly three or four) spongy radial arms on the margin of the disk, situated in its equatorial plane (with or without a connecting patagium between the arms).

Definition.— with two opposite spongy arms on the margin of the disk, without a connecting patagium.

The genus Spongolena opens the series of the Spongobrachida, or of the Spongodiscida provided with radial spongy arms on the margin of the disk. Spongolena is the most simple form of this subfamily, and bears only two simple opposite arms, without a connecting patagium. It corresponds to Amphibrachium (Porodiscida) and to Diplactura (Coccodiscida). Also there is no patagium. Spongolena may easily be confounded with Spongurus (compare my Prodromus, 1881, p. 461); but in the true Spongurus (an ellipsoid) the transverse section is circular, in Spongolena elliptical.

1. Spongolena rhopalura, n. sp.

Arms club-shaped, three times as long as broad, at the rounded distal end twice as broad as at the base, and twice as long as the diameter of the circular central disk. Surface nearly smooth.

Dimensions.—Radius of the arms (or the distance from the centre to the distal arm-end) 0.16, distal breadth 0.05, basal breadth 0.03.

Habitat.—Pacific, central area, Station 273, depth 2350 fathoms.

2. Spongolena spongura, n. sp.

Arms nearly cylindrical, twice as long as broad, and a little longer than the diameter of the elliptical central disk. Surface thorny, some longer bristle-shaped spines on the distal end of the