Definition.—Theocorida (vel Tricyrtida eradiata aperta), with cylindrical abdomen, and wide open truncate mouth. Cephalis without horn.
The genus Tricolocampe differs from its ancestral genus, Theocyrtis, in the loss of the cephalic horn; it has the same cylindrical form of the slender abdomen, and a wide open terminal mouth of the same breadth. The whole shell is more or less cylindrical, (sometimes conical in the upper part), with two distinct external strictures, or internal annular septa.
Subgenus 1. Tricolocampium, Haeckel.
Definition.—Pores of the thorax and of the abdomen of nearly equal size and similar form.
1. Tricolocampe cylindrica, n. sp. (Pl. [66], fig. 21).
Shell nearly cylindrical, smooth. Length of the three joints = 2 : 3 : 15, breadth = 3 : 4 : 5. Cephalis hemispherical, with numerous very small pores. Thorax and abdomen cylindrical, of about equal breadth, with equal, circular pores, disposed regularly in transverse rows, three to four rows in the thorax, ten to twelve in the abdomen. Mouth wide open, not constricted.
Dimensions.—Length of the three joints, a 0.02, b 0.03, c 0.15; breadth, a 0.03, b 0.04, c 0.05.
Habitat.—Central Pacific, Stations 265 to 274, depth 2350 to 2925 fathoms.
2. Tricolocampe pupa, Haeckel.
Eucyrtidium pupa, Ehrenberg, 1872, Abhandl. d. k. Akad. d. Wiss. Berlin, p. 293, Taf. vii. fig. 16.