Subgenus 1. Stichoperina, Haeckel.
Definition.—Shell with three solid radial ribs, or longitudinal dentate crests.
1. Stichopera ovata, n. sp.
Shell ovate, with three distinct strictures. Length of the four joints = 2 : 3 : 4 : 6. The fourth joint is the broadest, and twice as long as the second, with hemispherical basal pole. Cephalis hemispherical, with a conical horn of twice the length. Along the second and third joints descend three prominent divergent ribs, which disappear in the middle zone of the fourth joint. Pores regular, circular.
Dimensions.—Length of the shell (with four joints) 0.15, breadth 0.1. Length of the single joint, a 0.02, b 0.03, c 0.04, d 0.06.
Habitat.—Central Pacific, Station 266, depth 2750 fathoms.
2. Stichopera lagena, n. sp.
Shell bottle-shaped, with six sharp strictures; the upper half is slender, conical, and composed of six joints of nearly equal length, the lower half is formed only by the last subspherical joint. Cephalis subspherical, with a pyramidal horn of the same length. From its base arise three divergent ribs, which attain the greatest height in the fourth joint, and disappear in the sixth joint. (Similar to Stichophæna ritteriana, Pl. [75], fig. 12, but only with three ribs and seven joints.) Pores regular, hexagonal.
Dimensions.—Length of the shell (with seven joints) 0.25. Length of each joint 0.02 to 0.025, of the last joint 0.12; breadth 0.14.
Habitat.—Central Pacific, Station 272, depth 2600 fathoms.