Page:Scientific results HMS Challenger vol 18 part 1.djvu/504

296

Definition.—Network of the shell regular, with pores of equal size and similar form.

1. Ellipsoxiphus elegans, n. sp. (Pl. 14, fig. 7).

Proportion of the major axis of the ellipsoid to the minor = 5 : 4. Shell thick walled, with regular, circular meshes, separated by a regular, hexagonal elevated framework. From each hexagon-corner arises (between every three meshes) a short thin spine, about as long as the diameter of a mesh; twelve to fourteen meshes on the half equator, of the same breadth as the bars. Polar spines three-sided prismatic, cuspidate, about as long as the axis of the shell. (This elegant and not uncommon species is remarkable for its variations. By unequal development of both spines it passes over to Ellipsostylus.) In the figured variety (Pl. 14, fig. 7) the ends of the surface spines are connected by a very delicate network, so as to form an outer veil. This may further be separated as a peculiar genus Ellipsoxiphium palliatum.

Dimensions.—Longer axis 0.08 to 0.13, shorter axis 0.06 to 0.11; pores and bars 0.008; length of the polar spines 0.06 to 0.12, basal breadth 0.01.

Habitat.—Pacific, central area, Stations 270 to 274, from 2350 to 2925 fathoms.

2. Ellipsoxiphus flosculus, n. sp.

Proportion of the major axis to the minor = 6 : 5. Shell very thick walled, with regular, hexagonal meshes, eight to nine on the half equator, three to four times as broad as the bars. The inner contour of the meshes is circular, the outer six-lobed (similar to Xiphostylus phasianus, Pl. 13, fig. 9). Polar spines three-sided pyramidal, about as long as the major axis of the shell; their basal thickness equals one mesh.

Dimensions.—Longer axis 0.12, shorter axis 0.1; pores 0.012 to 0.015, bars 0.004; length of the polar spines 0.12 to 0.15, basal breadth 0.015.

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

3. Ellipsoxiphus fragilis, n. sp.

Proportion of the major axis to the minor = 4 : 3. Shell thin walled, with regular, circular meshes, twice as broad as the bars; ten to twelve on the half equator. Surface smooth. Polar spines cylindrical, at the apex conical, half as long as the major axis.

Dimensions.—Longer axis 0.16, shorter axis 0.12; pores 0.008, bars 0.004; length of the polar spines 0.09, basal breadth 0.008.

Habitat.—South Atlantic, Station 325, surface.

Definition.—Network of the shell irregular, with pores of different size or form.