The genus Archicorys and the following closely allied Cyrtocalpis differ from the two preceding genera in the ovate or urceolate form of the shell, which is more or less constricted towards the terminal mouth. The upper pole in Archicorys bears an apical horn, which is absent in Cyrtocalpis. The origin of these two genera may be the same, probably arising directly from Nassellida, and independently of the triradiate Cyrtoidea or bilocular Spyroidea. (Compare p. [1179].)
1. Archicorys galea, n. sp.
Shell smooth urceolate. Pores large, in the middle part hexagonal, towards both ends smaller and polygonal. Apical horn stout, three-sided pyramidal, half as long as the shell. Mouth with a short tubular peristome, about one-third as broad as the shell.
Dimensions.—Shell (without horn) 0.15 long, 0.12 broad; horn 0.07 long, mouth 0.05 broad.
Habitat.—Central Pacific, Station 272, depth 2600 fathoms.
2. Archicorys ampulla, n. sp.
Shell smooth, thin-walled, bottle-shaped, in the upper half conical, in the lower half inflate, subspherical. Pores subregular, circular, of the same breadth as the bars. Horn conical, stout, /about one-third as long as the shell. Mouth truncate, without peristome, about half as broad as the shell.
Dimensions.—Shell 0.15 long, 0.1 broad; horn 0.05, mouth 0.05.
Habitat.—Central Pacific, Station 268, depth 2900 fathoms.
3. Archicorys microstoma, n. sp. (Pl. [51], fig. 12).