Page:Scientific results HMS Challenger vol 18 part 1.djvu/502

294 four or five, smaller pores); eight to nine meshes on the half equator, these being twice to four times as broad as the bars.

Dimensions.—Longer axis of the shell 0.1, shorter axis 0.08; pores 0.007 to 0.01, bars 0.003.

Habitat.—Tropical zone of the Western Pacific, Station 225, surface.

Definition.— with simple ellipsoidal shell, with numerous radial spines on the surface, without polar spines or tubes.

The genus Ellipsidium differs from Cenellipsis solely in the development of numerous radial spines on the surface, and exhibits the same phylogenetic relation to it that Heliosphæra bears to Cenosphæra.

1. Ellipsidium pandanidium, n. sp.

Proportion of the longer axis of the ellipsoid to the shorter = 5 : 4. Shell thick walled, with regular and hexagonal meshes, twice as broad as the bars; eighteen to twenty on the half equator. In each hexagon-corner (between three pores) arises a short, three-sided pyramidal spine, half as long as the equatorial radius, and as thick at the base as a single mesh.

Dimensions.—Major axis of the ellipsoid 0.15, minor 0.12; pores 0.006, bars 0.003; length of the radial spines 0.03, basal breadth 0.006.

Habitat.—Fossil in the Tertiary rocks of Barbados (Haeckel).

2. Ellipsidium datura, n. sp.

Proportion of the longer axis of the ellipsoid to the shorter = 4 : 3. Shell thick walled, with regular, circular meshes, twice as broad as the thick bars between them eight to ten meshes on the half equator. Outer surface of the shell thorny, covered with short, conical, radial spines, which are regularly distributed (one spine between every three meshes), and about as long as the diameter of the meshes. (The shell is similar to the outer shell of Haliomma castanea, Haeckel, Monogr. d. Radiol., Taf. xxiv. fig. 4.)

Dimensions.—Major axis of the ellipsoid 0.12, minor axis 0.09; meshes 0.012, bars 0.006.

Habitat.—Western part of the Tropical Pacific, Station 225, depth 4475 fathoms.

3. Ellipsidium artocarpus, n. sp.

Proportion of the longer axis to the shorter = 3 : 2. Shell thick walled, with regular, circular meshes, separated by deep furrows, which represent a regular, hexagonal framework; on the half equator twelve to fifteen meshes, scarcely broader than the broad bars between them. Outer