Page:Scientific results HMS Challenger vol 18 part 2.djvu/409

Rh partly interrupted, longitudinal rows, separated by prominent crests. Mouth little constricted. Peristome with twenty to twenty-four broad, lamellar, pointed feet, which are about as long as the shell, little curved, and convergent.

Dimensions.—Cephalis 0.01 long, 0.04 broad; thorax 0.09 long, 0.09 broad.

Habitat.—North Pacific, Station 244, depth 2900 fathoms.

21. Carpocanium virgineum, n. sp. (Pl. 52, fig. 20).

Shell ovate, smooth, with flat perfectly hidden cephalis. Length of the two joints = 1 : 8, breadth = 3 : 9. Pores regular, circular, hexagonally framed, as broad as the bars, in about sixteen longitudinal rows on each side. Mouth little constricted. Peristome with eighteen to twenty-four very large, lamellar, pointed feet, which are longer than the shell, and so curved and convergent that their distal points come nearly in contact.

Dimensions.—Cephalis 0.01 long, 0.03 broad; thorax 0.08 long, 0.09 broad.

Habitat.—Central Pacific, Station 272, depth 2600 fathoms.

Definition.— with the basal mouth of the shell fenestrated (vel Dicyrtida multiradiata clausa).

Definition.— (vel Dicyrtida multiradiata clausa) with lateral apophyses. Cephalis with a horn.

The genus Sethophæna and the following Clistophæna form together the small subfamily of Sethophænida, comprising those Dicyrtida in which the thorax bears numerous radial appendages (four to six or more), and the mouth is closed by a lattice-plate. In Sethophæna the apophyses are lateral wings, as in Micromelissa, from which it may be derived by development of secondary wings, interpolated between the three primary wings.

1. Sethophæna tetraptera, n. sp.

Shell smooth, with deep collar stricture. Length of the two joints = 3 : 10, breadth = 4 : 9. Cephalis subspherical, without horn. Thorax ovate, with rounded hemispherical base, and subregular, hexagonal pores. From its upper half (below the collar stricture) arise four divergent,