Page:Scientific results HMS Challenger vol 18 part 2.djvu/880

1756 half times as long as the two lateral sides. Nasal odd style of each valve with ten to twelve pairs of branches, about twice as long as the four paired frontal and tergal styles, each of which bears five or six pairs. Terminal coronets three times forked, each with eight straight, spinulate, slightly divergent fingers, shaped like a human finger.

Dimensions.—Length of the shell 3.6, breadth 2.7.

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

3. Cœlodecas pentagona, n. sp.

Shell-mantle about as long as broad; its frontal perimeter nearly regular pentagonal, with five equal sides. Nasal odd style of each valve with six to eight pairs of branches scarcely longer than the four paired frontal and tergal styles, each of which is provided with four to six pairs. Terminal coronets irregularly branched, each with twelve to sixteen slender curved fingers, which bear at the distal end a spinulate knob.

Dimensions.—Length of the shell 2.6, breadth 2.4.

Habitat.—South Atlantic, Station 332, depth 2200 fathoms.

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

The genus Cœlostylus is characterised by the possession of twelve coronal styles; it is closely allied to Cœlospathis, and differs from this in the development of a new pair of styles on each valve. These are placed between the odd nasal and the odd sagittal style of each valve, they are directed forwards, and may therefore be called "pectoral styles."

1. Cœlostylus bisenarius, n. sp. (Pl. 126, fig. 3a, 3b).

Shell-mantle one and a third times as long as broad; its frontal perimeter pentagonal, with a deep median incision at the base; the two oral sides of the pentagon about as long as the basal odd side, and half as long as the two lateral sides. Sagittal perimeter (fig. 3a) octagonal; the three paired lateral sides of the bilateral octagon about equal, and somewhat shorter than the basal and oral odd sides. Equatorial perimeter rounded square. Nasal odd style of each valve with twelve alternate-cruciate pairs of lateral branches, about twice as long as the two paired pectoral styles (each with four pairs), and the odd sagittal style (with six pairs); the two paired tergal styles bear eight pairs and are longer than the latter, shorter than the nasal style. All styles are more or less curved, divergent, and at the distal end four times forked, bearing a terminal coronet with sixteen spinulate fingers (fig. 3b).

Dimensions.—Length of the shell 4.2, breadth 3.2.

Habitat.—Indian Ocean (Madagascar), Rabbe, surface.