Page:Scientific results HMS Challenger vol 18 part 1.djvu/393

Rh triangular spines is surrounded at the base by three small roundish pores (between the three wings of its base), and further by a coronal of six very large pores, three of which are pentagonal, and the other three (alternating) heptagonal. The six basal coronals are separated by irregular smaller pores. Medullary shell thin walled, with regular hexagonal pores (three on the radius) and thin bars, connected with the outer shell by six thin triangular prismatic radial beams, which are prolonged outside into short pyramidal spines (half as long as the radius).

Dimensions.—Diameter of the outer shell 0.2, thirty-six larger pores of the coronals 0.03 to 0.04, smaller pores between them 0.01 to 0.02, bars 0.005; inner shell 0.05 (with pores of 0.008); length of the spines 0.05, basal breadth 0.03.

Habitat.—South Atlantic, off Buenos Ayres, Station 323, depth 1900 fathoms.

19. Hexalonche pythagoræa, n. sp. (Pl. 22, fig. 1).

Cortical shell thick walled, smooth, three times as broad as the medullary shell. Pores irregular roundish, twice to eight times as broad as the bars, of very different size; usually in the space between every three spines are three or six larger pores, separated by numerous smaller pores (often the disposition of the larger pores is much more regular than in the figured specimen). Medullary shell with regular circular pores, connected with the outer by six very thin radial beams, which are prolonged outside into six short triangular pyramidal spines about as long and broad as the half radius.

Dimensions.—Diameter of the outer shell 0.12, pores 0.008 to 0.03, bars 0.004; inner shell 0.04; length of the spines 0.04, basal breadth 0.03.

Habitat.—Central Pacific, Station 271, depth 2425 fathoms.

20. Hexalonche aristarchi, n. sp. (Pl. 22, fig. 3).

Cortical shell thin walled, smooth, four times as broad as the medullary shell. Pores irregular polygonal, of very variable size and form, twice to six times as broad as the bars; six to ten on the radius. Medullary shell with regular hexagonal pores, connected with the outer by six very thin radial beams, which are prolonged outside into six triangular pyramidal spines, nearly as long as the radius.

Dimensions.—Diameter of the outer shell 0.1, pores 0.005 to 0.02, bars 0.003; inner shell 0.025; length of the spines 0.05, basal breadth 0.01.

Habitat.—North Pacific, Station 241, depth 2300 fathoms.

21. Hexalonche ekphantæa, n. sp.

Cortical shell thin walled, smooth, four times as broad as the medullary shell. Pores irregular roundish, of very variable size and form, twice to six times as broad as the bars, ten to fifteen on the radius. Six spines cylindro-conical, longer than the diameter of the shell.

Dimensions.—Diameter of the outer shell 0.2, pores 0.004 to 0.012, bars 0.002; inner shell 0.05; length of the spine 0.3, basal breadth 0.01.

Habitat.—Indian Ocean, Sunda Strait, surface, Rabbe.