Dimensions.—Diameter of the disk 0.16; length of the radial spines 0.18, basal breadth 0.003.
Habitat.—South Atlantic, Station 325, surface.
Subfamily 3. Spongobrachida, Haeckel, 1881, Prodromus, p. 461.
Definition.—Spongodiscida 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).
Genus 260. Spongolena,[[299]] n. gen.
Definition.—Spongodiscida 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.