Shell thick-walled, rough, with two slight strictures. Length of the three joints = 1 : 4 : 4, breadth = 1 : 3 : 1. Cephalis hemispherical, with a conical horn of the same length. Thorax ovate, in the upper half with three ribs, arising into short, triangular, slightly prominent wings. Abdomen prolonged into a cylindrical, narrow tube of the same length as the thorax. Terminal mouth very narrow. Pores subregular, circular.
Dimensions.—Length of the three joints, a 0.03, b 0.12, c 0.12; breadth, a 0.03, b 0.09, c 0.03.
Habitat.—Central Pacific, Station 265, depth 2900 fathoms.
13. Pterocorys pipetta, n. sp.
Shell thin-walled, smooth, with two slight strictures. Length of the three joints = 1 : 6 : 3, breadth = 1 : 3 : 1. Cephalis ovate, with a conical horn of twice the length. Thorax ovate, in the middle zone with three conical wings of the same length, curved slightly downwards (like those of Pterocorys columba, Pl. [71], fig. 2). Abdomen constricted into a cylindrical tube half as long as the thorax, with narrow mouth. Pores subregular, circular.
Dimensions.—Length of the three joints, a 0.02, b 0.12, c 0.06; breadth, a 0.02, b 0.06, c 0.02.
Habitat.—Tropical Atlantic, Station 347, depth 2250 fathoms.
Subgenus 3. Pterocorythium, Haeckel.
Definition.—Horn of the cephalis double or multiple. Abdomen not prolonged into a narrow tube.
14. Pterocorys rhinoceros, n. sp. (Pl. [71], fig. 1).