Shell smooth, with slight collar stricture. Length of the two joints = 1 : 4, breadth = 1 : 5. Cephalis subspherical, small, with a large, vertical, cylindrical horn, about as long as the shell, and small, circular pores. Thorax nearly three-sided pyramidal or tetrahedral, with three rounded edges and sub-regular, circular pores. Margin of the flat base with six conical, divergent, straight feet, somewhat shorter than the thorax. (Three on the corners, one on the middle of each side of the triangular base.)
Dimensions.—Cephalis 0.03 diameter, thorax 0.12 long, 0.14 broad.
Habitat.—North Pacific, Station 241, depth 2300 fathoms.
3. Clistophæna pyramidalis, n. sp.
Shell smooth, with slight collar stricture. Length of the two joints = 2 : 8, breadth = 3 : 10. Cephalis hemispherical, with a stout pyramidal horn of twice the length. Thorax six-sided pyramidal, with regular, circular pores of equal size, and six prominent, straight edges, which are prolonged into six divergent, pyramidal feet of half the length.
Dimensions.—Cephalis 0.02 long, 0.03 broad; thorax 0.08 long, 0.1 broad.
Habitat.—Central Pacific, Station 274, depth 2750 fathoms.
4. Clistophæna armata, n. sp. (Pl. [57], fig. 7).
Shell spiny, with deep collar stricture. Length of the two joints = 4 : 18, breadth = 5 : 15. Cephalis subspherical, with small, circular, hexagonally-framed pores, and a stout, three-sided prismatic, cuspidate horn of the same length. Thorax pear-shaped, with regular, circular pores and three pairs of stout pyramidal wings, placed in the three primary meridional planes of the collar beams; three of them lie in the upper, and three in the lower third of the thorax. Margin of the flat base with nine cylindrical, somewhat club-shaped, divergent feet.
Dimensions.—Cephalis 0.04 long, 0.05 broad; thorax 0.18 long, 0.15 broad.