Page:Scientific results HMS Challenger vol 18 part 2.djvu/574

1450 Dimensions.—Length of the shell (with eleven joints) 0.28, breadth 0.09; length of the tenth joint 0.02, of the last joint 0.1.

Habitat.—Central Pacific, Station 271, depth 2425 fathoms.

Definition.— (vel Stichocyrtida triradiata clausa) with three latticed lateral wings, or three longitudinal rows of lattice wings. Cephalis with a horn.

The genus Cyrtopera differs from the preceding Stichopera in the fenestration of the three lateral wings, and bears therefore to it the same relation that Sethornithium exhibits to Lithornithium among the Tricyrtida.

Definition.—Shell with three annular strictures and four joints.

1. Cyrtopera thoracoptera, n. sp. (Pl. 75, fig. 3).

Artopera thoracoptera, Haeckel, 1881, Prodromus et Atlas (loc. cit.).

Shell inflated, with three very deep strictures. Length of the four joints = 2 : 7 : 8 : 6. Cephalis hemispherical, with a slender, prismatic horn, half as long as the shell. Thorax subspherical, in its middle third with three latticed, triangular wings of half the length. Abdomen with inflated third, and inversely hemispherical fourth joint; the third is the broadest. Pores subregular, hexagonal, with thin bars.

Dimensions.—Length of the shell (with four joints) 0.23. Breadth of the third (broadest) joint 0.13. Length of the single joints, a 0.02, b 0.07, c 0.08, d 0.06.

Habitat.—Central Pacific, Station 266, depth 2750 fathoms.

2. Cyrtopera ornithoptera, n. sp.

Shell broadly ovate, with three slight strictures. Length of the four joints = 1 : 2 : 3 : 4. Cephalis hemispherical, with a slender, pyramidal horn of three times the length. Along the second and third joints arise with broad base three latticed, triangular wings, nearly as long as the whole shell. Abdomen inflated. The fourth joint is the broadest and longest, with hemispherical basal pole. Pores subregular, hexagonal. (Similar to Artopilium longicorne, Pl. 77, fig. 10, but with more closely reticulated network, and perfectly closed mouth.)

Dimensions.—Length of the shell (with four joints) 0.2. Breadth of the fourth (broadest) joint 0.14. Length of the single joints, a 0.02, b 0.04, c 0.06, d 0.08.

Habitat.—Central Pacific, Station 274, depth 2750 fathoms.