Both arms equal, three times as long as broad, thickened towards the truncated distal end, and armed with a strong pyramidal terminal spine. Each arm with seven joints, separated by convex, transverse septa, and halved by a radial beam lying in the longitudinal axis. Patagium incomplete, cylindrical, enveloping only the middle part of the shell.
Dimensions.—Radius of each arm 0.18, greatest breadth 0.06; transverse breadth of the patagium 0.08.
Habitat.—North Atlantic, Station 354, surface.
6. Amphymenium fusiforme, n. sp.
Both arms equal, lanceolate, three times as long as broad in the width, with seven to eight joints. Distal end pointed, armed with a strong conical terminal spine. Patagium complete, enveloping the whole shell with exception of the terminal spines. Whole form spindle-shaped.
Dimensions.—Radius of each arm 0.2, greatest breadth 0.07; transverse breadth of the patagium 0.15.
Habitat.—South Atlantic, Station 330, surface.
Genus 225. Amphirrhopalum,[[264]] Haeckel, 1881, Prodromus, p. 460.
Definition.—Porodiscida with two chambered arms, opposite in one axis, without a patagium; one arm or both forked at the distal end.
The genus Amphirrhopalum differs from Amphibrachium, its ancestral form, by bifurcation of the distal ends of the arms, which may affect either both arms, or only one of them.