Page:Scientific results HMS Challenger vol 18 part 1.djvu/450

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Definition.— with one medullary (intracapsular) and one cortical (extracapsular) shell, the two being connected by radial beams piercing the central capsule. Shell surface covered with branched radial spines.

The genus Elatomma differs from Haliomma in the ramification of the radial spines, and exhibits therefore the same relation to it that Cladococcus, among the Coscinommida, bears to Acanthosphæra.

Definition.—Pores of the cortical shell regular, of nearly equal size and similar form.

1. Elatomma pinetum, n. sp.

Cortical shell thick walled, with regular, circular, hexagonally framed pores, three times as broad as the bars. From its surface arise twenty to thirty large, three-sided prismatic, radial spines as long as the shell diameter, branched like a pine tree; on each edge of the spine five to six ramified branches, decreasing in size towards the distal end. Similar to Cladococcus pinetum (Pl. 27, figs. 1, 3), but differing in the possession of a medullary shell (one-third as large as the outer), with regular, circular pores, as broad as the bars.

Dimensions.—Diameter of the outer shell 0.2, inner 0.07; cortical pores 0.012, bars 0.004; length of the spines 0.2 to 0.24.

Habitat.—Central Pacific, Stations 266 to 272, surface.

2. Elatomma scoparium, n. sp.

Cortical shell thick walled, with regular, circular pores, twice as broad as the bars, connected with the medullary shell by twenty thin radial beams, which are prolonged outside into twenty large cylindrical radial spines somewhat longer than the radius; in the proximal half simple, in the distal half with six to nine dichotomous, irregular branches. Similar to Cladococcus scoparius (Pl. 27, fig. 2), but much larger, and with a large medullary shell (one-third as broad as the outer), and regular, circular pores.

Dimensions.—Diameter of the outer shell 0.12, inner 0.04; cortical pores 0.01, bars 0.005; length of the spines 0.08.

Habitat.—North Pacific, Station 240, surface.

Definition.—Pores of the cortical shell irregular, of different size or form.