Page:Scientific results HMS Challenger vol 18 part 2.djvu/879

Rh 3. Cœlospathis octodactyla, n. sp. (Pl. 128, fig. 9).

Shell-mantle about as long as broad, in the frontal perimeter nearly isosceles triangular, very similar to the two preceding species; it differs from them in the following characters: all eight styles have nearly equal size, and each bears six to eight pairs of branches. The eight fingers of the terminal coronets diverge nearly in one plane, and are not curved in a zigzag manner, but armed with alternate, slender, recurved hooks, which are larger than in the two preceding species, and geniculate at the base; the distal end of each finger bears a verticil of eight to ten very small divergent teeth, which are not recurved (fig. 9).

Dimensions.—Length of the shell 2.4, breadth 2.2.

Habitat.—North Pacific, Station 252, surface.

Definition.— with an odd sagittal frenulum on each galea and an outer lattice-mantle, armed with ten styles (one odd and four paired styles on each valve).

The genus Cœlodecas is closely allied to Cœlographis, but differs from it in the development of a new pair of styles on each valve. These are placed between the odd nasal and the paired tergal styles, are usually directed laterally, parallel to the frontal axis of the body, and may therefore be called frontal or lateral styles. The total number of coronal styles is therefore ten.

1. Cœlodecas sagittaria, n. sp. (Pl. 126, figs. 2a, 2b).

Shell-mantle one and a half times as long as broad; its frontal perimeter pentagonal, with a deep median incision at the base; the two oral sides of the pentagon twice as long as the two lateral sides, and one and a half times as long as the base. Sagittal perimeter ovate; equatorial perimeter subcircular. Nasal odd style of each valve with fourteen to sixteen pairs of branches, one and a half times as long as the paired frontal styles (each with eight to nine pairs), and twice as long as the paired tergal styles (each with four to six pairs of branches). Terminal coronets (on the free distal ends of the styles) richly branched, each with thirty to forty thorny fingers, which bear a conical point with recurved teeth, like an arrow.

Dimensions.—Length of the shell 3.2, breadth 2.1.

Habitat.—Tropical Atlantic, Station 347, depth 2250 fathoms.

2. Cœlodecas decastyla, n. sp.

Shell-mantle one and a third times as long as broad; its frontal perimeter pentagonal, with a slight incision on the base; the two oral sides of the pentagon as long as the base, and one and a