Definition.—Both arms of different size or form, with terminal spines.
8. Amphibrachium clavula, n. sp.
Both arms different in size and form; larger arm club-shaped, four times as long as broad, at the distal end three times as broad as at the base, and twice as long as the smaller arm, which resembles a stalked knob, with thin basal peduncle and spherical distal part. Ends of the two arms thorny (with numerous smaller, and three to five larger spines); one very large conical terminal spine on each pole of the main axis.
Dimensions.—Radius of the larger arm 0.3, of the smaller 0.15; distal breadth of the former 0.06, of the latter 0.04; basal breath 0.02.
Habitat.—South Atlantic, Station 333, surface.
Genus 224. Amphymenium,[[263]] Haeckel, 1881, Prodromus, p. 460.
Definition.—Porodiscida with two simple, undivided, chambered arms, opposite in one axis, connected by a patagium.
The genus Amphymenium differs from the preceding Amphibrachium, its ancestral form, by development of a patagium or connecticulum between both arms. This forms a latticed or more spongy envelop, which surrounds either the middle part of the shell, or the whole shell with exception of the distal ends of both arms. If the envelop become very spongy, the shell may be confounded with the cylindrical Ellipside Spongocore (nearly allied to Spongurus); possibly also Ommatogramma of Ehrenberg belongs to this genus.
Subgenus 1. Ommatogramma, Ehrenberg (?).
Definition.—Both opposite arms of the same size and form, blunt, without terminal spines.