Page:Scientific results HMS Challenger vol 18 part 1.djvu/438

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Definition.— with two concentric spherical lattice-shells, united by radial beams.

Definition.— with one medullary (intracapsular) and one cortical (extracapsular) shell, which are connected by radial beams, piercing the central capsule. Shell surface covered with simple radial spines of the same kind.

The genus Haliomma, one of the oldest known Radiolarian genera, contained in the catalogue of its discoverer, Ehrenberg, a large number of very different, belonging to at least sixteen different genera. We limit here the conception of the genus to those Haliommida which bear simple radial spines of one kind on the surface of the cortical shell (the latter being separated from the medullary shell by the central capsule).

Definition.—Pores of the cortical shell regular, of nearly equal size and similar form; spines on the whole surface (commonly one spine at each nodal-point).

1. Haliomma hexagonium, n. sp.

Cortical shell four times as broad as the medullary shell, both having very thin thread-like bars, and regular, hexagonal pores (eighteen to twenty on the radius of the outer, five to six on the radius of the inner shell). The two shells connected by twenty thin thread-like radial beams. At each nodal-point of the outer shell arises a bristle-shaped radial spine, half as long as the radius. (Similar to Heliosoma radians, Pl. 28, fig. 3, but with all the spines equal.)

Dimensions.—Diameter of the outer shell 0.2, inner 0.05; pores of the outer 0.015, of the inner 0.01; length of the spines 0.05.

Habitat.—Equatorial Atlantic, Station 347, surface.

2. Haliomma arachnium, n. sp.

Cortical shell three times as broad as the medullary shell; pores of the former regular, hexagonal, with very thin thread-like bars (fourteen to sixteen on the radius); pores of the latter regular,