Page:Scientific results HMS Challenger vol 18 part 1.djvu/540

332 1. Xiphatractus armadillo, n. sp. (Pl. 17, fig. 11).

Cortical shell thick walled, smooth, with regular, circular pores, about as broad as the bars; fifteen to sixteen on the half equator. Polar spines three-sided pyramidal, with thick, prominent edges, of irregular form; the longer about as long as the main axis, the shorter scarcely one-third as long; their basal breadth equals the diameter of the inner medullary shell.

Dimensions.—Major axis of the cortical shell 0.13, minor axis 0.1, thickness of its wall 0.01; pores and bars 0.005; main axes of the two medullary shells 0.07 and 0.03; length of the major polar spine 0.12, of the minor 0.04, basal thickness 0.04.

Habitat.—Pacific, central area, Station 272, depth 2600 fathoms.

2. Xiphatractus euphractus, n. sp.

Cortical shell thick walled, smooth, with regular, circular pores, twice as broad as the bars; eight to nine on the half equator. Each pore has six to nine excisions (commonly eight), elegantly lobed, flower-like (as in Xiphostylus phasianus, Pl. 13, fig. 9). Polar spines strong, angulate; the major pyramidal, longer than the main axis, the shorter elegantly pommel-like, scarcely one-third as long.

Dimensions.—Major axis 0.15, minor 0.12; pores 0.014, bars 0.007; main axes of the two medullary shells 0.09 and 0.05; length of the larger polar spine 0.16, of the shorter 0.05, greatest thickness 0.03.

Habitat.—South Atlantic, Station 332, depth 2200 fathoms.

Definition.—Network of the cortical shell regular or subregular, with meshes of nearly equal size and similar form; surface thorny or papillose.

3. Xiphatractus spinulosus, Haeckel.

Stylosphæra spinulosa, Ehrenberg, 1875, Abhandl. d. k. Akad. d. Wiss. Berlin, p. 84, Taf. xxv. fig. 8.

Cortical shell thin walled, with spiny surface, and large, regular, circular pores, four times as broad as the bars; seven to eight on the half equator. Spines between the pores of the same size, conical. Polar spines also conical, but much larger; the major about as long as the main axis, the minor scarcely half as long; their basal thickness equals the largest pores.

Dimensions.—Major axis 0.1, minor 0.08; pores 0.012, bars 0.003; diameter of the spherical medullary shells 0.06 and 0.03; length of the major polar spine 0.09, of the minor 0.04, basal thickness 0.02.

Habitat.—Fossil in the Tertiary rocks of Barbados.