Definition.—Zygospyrida with three basal feet, without apical horn.
The genus Tristylospyris exhibits in general the same structure as the typical genus Tripospyris, its ancestral form. It differs from the latter in the absence of the apical horn, which is completely reduced, and may therefore be regarded as the simplest prototype of all tripodal Cyrtellaria without a horn.
Subgenus 1. Tristylospyrula, Haeckel.
Definition.—Feet simple, not branched nor forked.
1. Tristylospyris palmipes, n. sp. (Pl. [84], fig. 14).
Shell companulate, smooth, with slight sagittal stricture. Pores irregular roundish, three pairs of larger annular pores on each side of the broad ring. Basal plate with four large collar pores. Feet half as long as the shell, slightly divergent, straight, prismatic, with a broad, hand-like, radially striped plate at the distal end.
Dimensions.—Shell 0.1 long, 0.09 broad; feet 0.06 long.
Habitat.—Equatorial Atlantic, Station 347, depth 2250 fathoms.
2. Tristylospyris scaphipes, n. sp. (Pl. [84], fig. 13).
Shell nut-shaped, smooth, with sharp sagittal stricture. Pores very small and numerous, circular; two pairs of larger pores on both sides of the ring. Basal plate with four large pores (?). Feet about half as long as the shell, angular, shovel-shaped, straight, parallel, vertical.