Page:Scientific results HMS Challenger vol 18 part 2.djvu/539

Rh peristome, so that the inflated abdomen is broader than the terminal mouth. They represent, therefore, the transition to the Theocapsida, with closed mouth. The abdomen is commonly more or less ovate or barrel-shaped, sometimes inversely conical. The cephalis of Theocorys bears a single apical horn.

Definition.—Pores of the thorax and of the abdomen of nearly equal size and similar form.

1. Theocorys turgidula, Haeckel.

Eucyrtidium turgidulum, Ehrenberg, 1872, Abhandl. d. k. Akad. d. Wiss. Berlin, p. 293, Taf. vii. fig. 13.

Shell slender, ovate, with two deep strictures, very fragile and thin-walled. Length of the three joints = 2 : 5 : 7, breadth = 2 : 6 : 6. Cephalis subspherical, with a pyramidal horn of the same length. Thorax nearly spherical. Abdomen ovate, twice as broad as the constricted mouth. Pores very numerous, regular hexagonal, three to four times as broad as the bars.

Dimensions.—Length of the three joints, a 0.015, b 0.05, c 0.07; breadth, a 0.02, b 0.06, c 0.06.

Habitat.—Tropical Pacific (Philippine Sea), Stations 206 and 224, surface.

2. Theocorys veneris, n. sp. (Pl. 69, fig. 5).

Shell inversely ovate, with two deep strictures, smooth. Length of the three joints = 2 : 5 : 6, breadth = 3 : 7 : 6. Cephalis hemispherical, with a slender conical horn of twice the length. Thorax nearly spherical. Abdomen ovate, twice as broad as the constricted mouth. Pores regular, circular, twice as broad as the bars, quincuncially disposed.

Dimensions.—Length of the three joints, a 0.02, b 0.05, c 0.06; breadth, a 0.03, b 0.07, c 0.06.

Habitat.—Cosmopolitan; Atlantic, Indian, Pacific; many Stations, surface.

3. Theocorys cretica, Haeckel.

Eucyrtidium creticum, Ehrenberg, 1872, Abhandl. d. k. Akad. d. Wiss. Berlin, p. 291, Taf. xi. fig. 23.

Shell ovate, thin-walled, smooth, with two deep strictures. Length of the three joints = 2 : 4 : 4, breadth = 3 : 6 : 6. Cephalis hemispherical, with a conical horn of the same length. Thorax and abdomen nearly hemispherical, inflated, united by the opposite bases of the hemispheres. Constricted mouth only one-third as broad as the abdomen. Pores very small and numerous, regular, circular, of the same breadth as the bars, quincuncially disposed.

Dimensions.—Length of the three joints, a 0.02, b 0.04, c 0.04; breadth, a 0.03, b 0.06, c 0.06.

Habitat.—Mediterranean, Crete, Corfu, surface.