Cortical shell lentelliptical, its breadth (or transverse axis) surpassing considerably the length (or the principal axis). Surface thorny and somewhat hump-backed. The spiral wings of the transverse girdle have about the same breadth as the eight internal gates between them and the axial beams.
Dimensions.—Length of the cortical shell (or principal axis) 0.15, breadth (or transverse axis) 0.2; length of the medullary shell 0.05, breadth 0.04.
Habitat.—South Atlantic, west of Tristan da Cunha, Station 332, depth 2200 fathoms.
2. Spironium diagonale, n. sp.
Cortical shell nearly spherical, four times as great as the subspherical medullary shell. Surface rough. The spiral wings of the transverse girdle about half as broad as the eight internal gates between them and the axial beams.
Dimensions.—Diameter of the cortical shell 0.16, of the medullary shell 0.04.
Habitat.—Indian Ocean, Zanzibar, Pullen, depth 2200 fathoms.
Subgenus 2. Spironilla, Haeckel.
Definition.—Surface of the shell covered with simple or branched radial spines.
3. Spironium spinosum, n. sp.