Page:Scientific results HMS Challenger vol 18 part 2.djvu/636

1512

Definition.— (vel Stichocyrtida eradiata clausa) with an apical horn on the cephalis, without basal terminal spine.

The genus Cyrtocapsa and the two following genera represent together the small subfamily of Stichocapsida, or of those in which the many-jointed shell bears no radial appendages, and the terminal mouth is closed by a lattice-plate. They have been derived from the Stichocorida by development of such a closing plate. Cyrtocapsa bears an apical horn on the cephalis, and may be derived therefore directly from Eucyrtidium.

Definition.—Shell with three annular strictures (or internal septa) and four distinct joints.

1. Cyrtocapsa tetrapera, n. sp. (Pl. 78, fig. 5).

Shell rough, pear-shaped, with three deep strictures. The three first joints are of equal lengths, and each half as long as the hemispherical fourth joint. Cephalis subspherical, with an oblique conical horn of the same length. The third joint is the broadest, three times as broad as long. Pores regular, circular.

Dimensions.—Length of the shell (with four joints) 0.15, breadth 0.09; length of each of the three first joints 0.03, of the last 0.06.

Habitat.—Western Tropical Pacific, Station 225, depth 4475 fathoms.

2. Cyrtocapsa compacta, n. sp. (Pl. 77, fig. 8).

Eucyrtidium compactum, Haeckel, 1878, Atlas, loc. cit.

Shell rough, pear-shaped, with three slight strictures. The hemispherical cephalis bears a thick pyramidal spine of the same length, and is half as long as the second and the third joints, one-third as long as the hemispherical fourth joint. The third joint is the broadest, three times as broad as long. Pores subregular, circular. In the centre of the basal pole is one larger pore, the remnant of the constricted mouth of Eucyrtidium.

Dimensions.—Length of the shell (with four joints) 0.16, breadth 0.12. Length of the single joints, a 0.02, b 0.04, c 0.04, d 0.06.

Habitat.—Western Tropical Pacific, Station 206, depth 2100 fathoms.