Page:Scientific results HMS Challenger vol 18 part 1.djvu/530

322 9. Lithatractus rosetta, n. sp.

Outer shell thick walled, thorny, with regular network; meshes circular, funnel-shaped, its outer aperture elegant, rosette-like, with eight to ten incisions (like Stylosphæra calliope, Pl. 16, fig. 6); eight to ten meshes on the half equator, three to four times as broad as the bars. Proportion of the longer axis to the shorter = 5 : 4. Shorter axis equals three times the diameter of the inner spherical shell. Polar spines three-sided pyramidal, about half as long as the shorter axis, as broad at the base as a mesh.

Dimensions.—Longer axis of the cortical shell 0.15, shorter 0.12; pores 0.02, bars 0.005; length of the polar spines 0.05, basal breadth 0.02; diameter of the inner shell 0.04.

Habitat.—South-eastern part of the Pacific, Station 302, depth 1450 fathoms.

Definition.—Network of the outer shell irregular, with meshes of unequal size or dissimilar form; surface smooth, without thorns or papillæ.

10. Lithatractus conifer, n. sp.

Outer shell thin walled, smooth, with irregular, roundish pores, two to four times as broad as the thin bars; fifteen to twenty on the half equator. Margin of the pores simple. Proportion of the major axis to the minor = 3 : 2. Minor axis twice as large as the diameter of the inner spherical shell, the pores of which are also irregular, roundish, but of half the size. Polar spines conical, somewhat shorter than the main axis, on the base two to three times as thick as a large pore.

Dimensions.—Longer axis of the outer shell 0.15, shorter axis 0.1; pores 0.002 to 0.004, bars 0.001; diameter of the inner shell 0.05; length of the polar spines 0.12, basal breadth 0.012.

Habitat.—South Atlantic, Station 325, surface.

11. Lithatractus lobatus, n. sp.

Outer shell thick walled, smooth, with irregular, roundish pores, four to eight times as broad as the bars; six to eight on the half equator. Margin of the pores lobed, very irregular, bluntly dentate, by five to twenty slight incisions. Proportion of the major axis to the minor very variable, between 3 : 2 and 9 : 8. Diameter of the inner shell also variable, between one-third and one-half of the outer; pores of the former scarcely half the size of the latter, simple, roundish, or circular. The inner shell is at some parts quite spherical, at other parts more or less ellipsoidal. Polar spines conical, very variable in size and form, sometimes in the basal half triangular; they are sometimes somewhat longer than the main axis, at other times considerably shorter; their basal breadth is occasionally the same as that of the largest pores, sometimes, however, scarcely half as large. This deep-sea species is very common in the central area of the Tropical Pacific (Stations 266 to 272), and occurs also fossil in the Barbados deposits. It is interesting from its great variability, and sometimes constitutes a transitional form to Stylosphæra.