Page:Scientific results HMS Challenger vol 18 part 1.djvu/451

Rh 3. Elatomma juniperinum, n. sp. (Pl. 28, fig. 8).

Cortical shell thin walled, with regular, polygonal, or roundish pores, twice to four times as broad as the bars, connected with the small medullary shell by about twenty thin radial beams. Inner shell only one-eighth as broad as the outer, with few irregular, polygonal meshes. Surface covered with very numerous (one hundred to one hundred and fifty or more) branched conical radial spines, one-third as long as the shell radius, with six to twelve short lateral branches.

Dimensions.—Diameter of the outer shell 0.2, inner 0.025; cortical pores 0.08 to 0.016, bars 0.004; length of the spines 0.04.

Habitat.—Central Pacific, Station 271, surface.

4. Elatomma penicillus, n. sp.

Cortical shell thin walled, with irregular, polygonal pores, twice to four times as broad as the bars, connected with the medullary shell by twenty (or more?) very thin beams. These are prolonged outside into twenty straight, three-sided prismatic, radial spines as long as the radius, with a brush-like bunch of six to nine short, irregularly ramified branches at the end. Medullary shell very delicate (half as broad as the outer), with regular, hexagonal meshes and thread-like bars.

Dimensions.—Diameter of the outer shell 0.15, inner 0.08; length of the spines 0.08.

Habitat.—West coast of Norway, Bergen, Haeckel.

5. Elatomma irregulare, n. sp.

Cortical shell thin walled, with irregular, polygonal, or roundish meshes, twice to six times as broad as the bars; the medullary shell of the same structure, half as broad, with smaller irregular pores. Forty to sixty curved, three-sided, radial spines, as long as the shell, with a bunch of very irregular, curved, and partly ramified branches at the distal end.

Dimensions.—Diameter of the outer shell 0.2, inner 0.1; length of the spines 0.2, breadth 0.01.

Habitat.—North Atlantic, Gulf Stream, Færöe Channel, surface, John Murray.

Definition.— with two extracapsular cortical shells without by-spines, connected by long prismatic radial spines.

The genus Leptosphæra, together with the three following genera, forms the very peculiar and typical small group of which we call the Diplosphærida (with four genera and twenty-four species); their shell is composed of two concentric spheres as in the three foregoing genera; but whilst in these the inner shell is an intracapsular medullary shell and the outer an extracapsular cortical shell, in the Diplosphærida