Definition.—Basal feet simple, neither forked nor branched.
1. Tholospyris tripodiscus, n. sp. (Pl. [89], fig. 1).
Shell campanulate, smooth, as broad as long, with deep sagittal stricture. Cephalis compressed, with irregular roundish pores; two or three pairs of larger annular pores on each side of the ring. Basal plate with four large pores. Galea with two very large opposite holes (an occipital and a frontal opening). A slender free perpendicular columella connects the uppermost part of the sagittal ring with the strong three-sided pyramidal apical horn. All three feet of equal length, half as long as the ring, three-sided, prismatic, divergent, with three dentated edges.
Dimensions.—Shell 0.13 diameter, ring 0.08 long, feet 0.05 long.
Habitat.—Central Pacific, Station 272, depth 2600 fathoms.
2. Tholospyris fenestrata, n. sp. (Pl. [89], fig. 2).
Shell roundish polyhedral, smooth, with slight sagittal stricture. Cephalis nearly cubical, with irregularly roundish pores; two or three pairs of larger pores on each side of the ring. Basal plate with two very large pores. Galea pyramidal, with two large occipital holes. Columella enclosed in the dorsal wall of the galea, prolonged into an oblique pyramidal spine of the same length. Two pectoral feet pyramidal, nearly vertical and as long as the ring, twice as long as the caudal foot.
Dimensions.—Shell 0.12 diameter, ring 0.07, pectoral feet 0.05 long.
Habitat.—Central Pacific, Station 266, depth 2750 fathoms.
3. Tholospyris galeata, n. sp.