Page:Scientific results HMS Challenger vol 18 part 2.djvu/425

Rh 8. Sethocyrtis cassis, Haeckel.

Cornutella cassis, Ehrenberg, 1854, Mikrogeol., Taf. xxii. fig. 38.

Cyrtocalpis cassis, Haeckel, 1862, Monogr. d. Radiol., p. 287.

Shell pear-shaped, smooth, with obliterated collar stricture. Length of the two joints = 4 : 13, breadth = 3 : 12. Cephalis ovate, with a conical horn of half the length. Thorax inflate, ovate, with subregular, circular, quincuncial pores, twice to three times as broad as the bars. Mouth constricted, truncate, two-thirds as broad as the thorax, without prominent peristome.

Dimensions.—Cephalis 0.04 long, 0.03 broad; thorax 0.13 long, 0.12 broad.

Habitat.—Fossil in Tertiary rocks of Sicily (Caltanisetta).

Definition.— (vel Dicyrtida eradiata aperta) with ovate or sub-cylindrical thorax, the mouth of which is constricted and prolonged into a ring-like peristome. Cephalis with an apical horn.

The genus Sethocorys differs from the preceding Sethocyrtis, its ancestral form, in the form of the constricted mouth, which is prolonged into a prominent, hyaline, tubular, or annular peristome.

1. Sethocorys achillis, n. sp. (Pl. 62, fig. 8).

Shell rough, pear-shaped, with distinct collar stricture. Length of the two joints = 4 : 8, breadth = 3 : 8. Cephalis ovate, with a stout pyramidal horn of half the length. Thorax nearly spherical, with regular, circular, quincuncial pores of the same breadth as the cephalic pores. Mouth constricted, half as broad as the thorax, with a broad, smooth, striated peristome.

Dimensions.—Cephalis 0.04 long, 0.03 broad; thorax 0.08 long, 0.08 broad.

Habitat.—Cosmopolitan; Mediterranean (Corfu), Atlantic, Indian, Pacific; many stations, at various depths.

2. Sethocorys patrocli, n. sp.

Shell thorny, pear-shaped, with slight collar stricture. Length of the two joints = 4 : 12, breadth = 3 : 10. Cephalis ovate, with a pyramidal horn of twice the length. Thorax ovate, truncate at both poles, with regular, circular pores, twice as broad as the cephalic pores. Mouth constricted, half as broad as the thorax, with a broad, smooth, prominent peristome.

Dimensions.—Cephalis 0.04 long, 0.03 broad; thorax 0.12 long, 0.1 broad.

Habitat.—Central Pacific, Stations 263 to 274, depth 2350 to 3000 fathoms.