Page:Scientific results HMS Challenger vol 18 part 1.djvu/277

Rh the central point of the shell are united about twelve (?) thin and straight radial beams, which are forked, with dichotomous branches; the distal ends of the branches are inserted in the corners of the hexagons on the inside of the shell.

Dimensions.—Diameter of the shell 0.15, pores 0.02, bars 0.003.

Habitat.—Central Pacific, Station 271, surface.

Definition.— with one single latticed sphere, with simple shell-cavity; with shell-pores which are prolonged on the outside in centrifugal, conical, or cylindrical tubuli.

The genus Ethmosphæra differs from the simple Cenosphæra, its ancestral form, by the peculiar formation of the shell-pores; in all observed species of the genus these are quite regular, of nearly equal size and form; their base in the spherical shell-face is hexagonal, but on the outside prolonged into centrifugal, external, radial tubuli, which are either conical or cylindrical (in the latter case both openings of the tubes being equal, in the former the outer opening being smaller than the inner). The solitary Ethmosphæra corresponds to the social Siphonosphæra; but in the former the formation of the shell and of its tubuli is quite regular, in the latter more or less irregular.

Definition.—Tubuli conical, their outer opening smaller than the inner.

1. Ethmosphæra siphonophora, Haeckel.

Ethmosphæra siphonophora, Haeckel, 1862, Monogr. d. Radiol., p. 350, Taf. xi. fig. 1.

Tubuli conical, their outer opening half as broad as the inner and three times as broad as their height. Five to six pores on the quadrant. Diameter of the outer pores one and a half times as large as their distance from each other.

Dimensions.—Diameter of the shell 0.1, outer pores 0.01, their distance 0.007.

Habitat.—Mediterranean (Messina), surface, Haeckel.

2. Ethmosphæra conosiphonia, n. sp. (Pl. 12, figs. 5, 5a).

Tubuli conical, their outer opening two thirds as broad as the inner, and scarcely broader than their height. Ten to twelve pores on the quadrant. Diameter of the outer pores twice as large as their distance from each other.

Dimensions.—Diameter of the shell 0.17, outer pores 0.01, their distance 0.005.

Habitat.—Central Pacific, Station 268, depth 2900 fathoms.