Shell hemispherical, nearly twice as broad as long, smooth. Pores irregular, roundish, twice to four times as broad as the bars. Mouth wide open. Apical horn spindle-shaped, half as long as the shell. Three feet cylindrical, nearly straight and parallel, as long as the shell, forked at the distal end. (Exhibits an external similarity to _Tripospyris semantis_, Pl. 84, fig. 2, but has no trace of sagittal ring and constriction, and the simple shell-cavity has a wide open mouth.) _Dimensions._--0.06 long, 0.1 broad; horn 0.03 long, feet 0.07 long. _Habitat._--North Pacific, Station 241, depth 2300 fathoms. 9. _Tripilidium cladopodium_, n. sp. Shell campanulate, rough, about as long as broad. Pores subregular, circular, as broad as the bars. Mouth slightly constricted. Apical horn and three divergent feet of nearly equal size and form, three-sided prismatic, straight and stout, irregularly dentate and branched, somewhat longer than the shell. _Dimensions._--Shell 0.08 diameter; horn and feet 0.1 to 0.12 long. _Habitat._--Central Pacific, Station 265, depth 2900 fathoms. {1143}Genus 502. _Tripodiscium_,[119] Haeckel, 1881, Prodromus, p. 428. _Definition._--#Archipilida# (vel Monocyrtida triradiata aperta) without lateral ribs and apical horn, with three simple or branched terminal feet. The genus _Tripodiscium_ may be derived either from the preceding _Tripilidium_ by loss of the apical horn, or from the nearly related _Tristylospyris_ by loss of the sagittal ring and constriction. Some forms of the latter genus can scarcely be distinguished from similar species of the former. Subgenus 1. _Tripodiscinus_, Haeckel. _Definition._--Feet simple, not branched nor forked. 1. _Tripodiscium tristylospyris_, n. sp. Shell subspherical, with regular, circular pores, twice as broad as the bars. Mouth constricted, half as broad as the shell, with three short spindle-shaped feet, which are nearly parallel and vertical, half as long as the shell. (Similar to _Tristylospyris scaphipes_, Pl. 84, fig. 13, but without sagittal ring and constriction.) _Dimensions._--Shell 0.08 long, 0.07 broad; feet 0.04 long. _Habitat._--Central Pacific, Station 265, depth 2900 fathoms. 2. _Tripodiscium ovatum_, n. sp. Shell ovate, rough, nearly as broad as long. Pores regular circular, double-contoured, twice as broad as the bars. Mouth constricted, one-third as broad as the shell, with three convergent short triangular feet. _Dimensions._--Shell 0.1 long, 0.09 broad; feet 0.02 long. _Habitat._--Central Pacific, Station 271, depth 2425 fathoms. 3. _Tripodiscium clavatum_, n. sp. Shell ovate, smooth, one and a half times as long as broad. Pores irregular roundish, of different sizes. Mouth constricted, two-thirds as broad as the shell, with three divergent, straight club-shaped feet, nearly as long as the shell. _Dimensions._--Shell 0.12 long, 0.08 broad; feet 0.1 long. _Habitat._--Tropical Atlantic, Station 348, depth 2450 fathoms.