Definition.—Basal plate with two large pores only (the primary jugular pores of Semantis).
1. Tripospyris cortina, n. sp. (Pl. [95], fig. 1).
Shell ovate, smooth, about as long as broad, with slight ovate sagittal stricture, and broad primary ring in its wall. Basal plate with two large kidney-shaped collar pores only (cardinal pores). Facial and occipital plates each with two pairs of large annular pores, and ten to twelve pairs of small lateral pores. Apical horn and the three basal feet of equal length, one and a half times as long as the shell, three-sided prismatic, straight, divergent.
Dimensions.—Shell 0.08 long, 0.09 broad; horn and feet 0.15 long.
Habitat.—Central Pacific, Station 271, depth 2425 fathoms.
2. Tripospyris cortiniscus, n. sp. (Pl. [84], fig. 6).
Shell ovate, smooth, one and a third times as long as broad, with sharp ovate sagittal stricture and broad primary ring. Basal plate with two large cardinal pores only. Occipital plate with two pairs of very large pores; facial plate and lateral sides with numerous smaller irregular roundish pores. Apical horn small, conical, curved, half as long as the three basal feet, which are club-shaped and three-edged, with thinner bases and half as long as the shell, strongly divergent.
Dimensions.—Shell 0.12 long, 0.09 broad; horn 0.03 long, feet 0.06 long.
Habitat.—Central Pacific, Station 266, depth 2750 fathoms.
3. Tripospyris semantis, n. sp. (Pl. [84], figs. 2, 3).