Dimensions.—Cephalis 0.04 long, 0.04 broad; thorax 0.05 long, 0.05 broad.
Habitat.—Central Pacific, Stations 265 to 268, depth 2700 to 2900 fathoms; also fossil in Barbados.
Genus 578. Dictyocephalus,[[195]] Ehrenberg, 1860, Monatsber. d. k. preuss. Akad. d. Wiss. Berlin, p. 830.
Definition.—Sethocorida (vel Dicyrtida eradiata aperta) with ovate or subcylindrical thorax, the mouth of which is more or less constricted, either truncate or with a ring-like peristome. Cephalis rounded, without horn.
The genus Dictyocephalus has originated probably from Sethocorys by reduction and loss of the apical horn. The mouth is more or less constricted, either simple, truncate (Dictyocryphalus), or provided with a prominent, broad, hyaline, annular peristome (Dictyoprora).
Subgenus 1. Dictyoprora, Haeckel, 1881, Prodromus, p. 430.
Definition.—Mouth of the thorax constricted, with a prominent, ring-like or tubular, hyaline peristome.
1. Dictyocephalus amphora, n. sp. (Pl. [62], fig. 4).
Shell smooth, thick-walled, subovate, with slight collar stricture. Length of the two joints = 5 : 9, breadth = 6 : 8. Cephalis large, obtusely conical, with numerous oblique pore-canals. Thorax inflate, with six to eight transverse rows of roundish pores, increasing in size towards the base. Mouth constricted, one-third as broad as the thorax, with an internal diaphragm and a narrow hyaline peristome.
Dimensions.—Cephalis 0.05 long, 0.06 broad; thorax 0.09 long, 0.08 broad.