Subgenus 1. Tholospirema, Haeckel.
Definition.—Spiral convolutions or turns of the cortical shell simple, only one single wing of the sagittal girdle turning around the transverse axis.
1. Tholospira nautiloides, n. sp.
Cortical shell with smooth surface, five times as long as the lentelliptical medullary shell. Perimeter of the lateral plane elliptical, one and a half times as long as broad. Four internal kidney-shaped gates (between the lateral wings of the transverse girdle, as in Tetrapyle). One wing of the sagittal girdle turns around the other in two to two and a half simple spiral turns.
Dimensions.—Length of the cortical shell 0.24, breadth 0.18; length of the medullary shell 0.05, breadth 0.04.
Habitat.—Indian Ocean, between Ceylon and Socotra, Haeckel, surface.
2. Tholospira spinosa, n. sp.
Cortical shell covered with numerous (sixty to eighty or more) simple, bristle-like radial spines, about the length of the shell. Perimeter of the lateral plane nearly quadrangular, with four rounded corners (on the poles of two crossed diagonal axes), one and a half times as long as broad. Eight internal egg-shaped gates (between the lateral wings of the transverse girdle and two axial beams in the principal axes, as in Octopyle). One wing of the sagittal girdle turns around the other in two to three simple spiral turns.
Dimensions.—Length of the cortical shell 0.27, breadth 0.18; length of the medullary shell 0.04, breadth 0.03.
Habitat.—South Pacific, Station 288, surface.