Shell irregular, clustered, or tuberous, composed of twenty to thirty irregular, roundish chambers of very different size, the largest four to eight times as broad as the smallest, aggregated without order around a central, lentelliptical, Larnacilla-shaped medullary shell. Pores irregular, roundish, twice to four times as broad as the bars. Surface smooth or a little spiny.
Dimensions.—Diameter of the whole shell 0.18, of the central Larnacilla-shell 0.05.
Habitat.—Pacific, central area, Station 266, depth 2750 fathoms.
2. Sorolarcus tetrapylifer, n. sp.
Shell irregularly roundish, clustered, composed of ten to twelve irregular rather long chambers of almost uniform size, the largest twice as broad as the smallest, aggregated without order around a central shell of the structure of Tetrapyle, which encloses an inner trizonal Larnacilla-shell of half the size. Pores irregular, roundish, twice to four times as broad as the bars. Surface spiny.
Dimensions.—Diameter of the whole shell 0.25, of the outer (Tetrapyle-like) medullary shell 0.12, of the inner (Larnacilla-like) shell 0.06.
Habitat.—Pacific, central area, Station 272, depth 2600 fathoms.
Subgenus 2. Sorolarcidium, Haeckel.
Definition.—Shell with radial spines.
3. Sorolarcus terminalis, n. sp.