Page:Scientific results HMS Challenger vol 18 part 1.djvu/374

166 Dimensions.—Diameter of the outer shell 0.24, middle 0.06, inner 0.02; cortical pores 0.007 to 0.015, bars 0.004; length of the spines 0.12.

Habitat.—Central Pacific, Station 274, depth 2750 fathoms.

Definition.— with four concentric spherical lattice-shells.

Definition.— with four concentric lattice-spheres and four crossed, equal, simple spines.

The genus Staurocromyum has arisen probably from Stauracontium by duplication of the cortical shell, two concentric shells lying within, two others outside the central capsule.

1. Staurocromyum quadruplex, n. sp.

Radial proportion of the four spheres = 1 : 2 : 8 : 10. Both medullary shells with very small, regular, circular pores. Inner cortical shell with regular, circular, hexagonally-framed pores, twice as broad as the bars; from each hexagon-corner arises a small by-spine, and these, connected by tangential branches at equal distances from the centre, form the delicate outer cortical shell, with spiny surface. Four main spines three-sided pyramidal, as long as the shell radius.

Dimensions.—Diameter of the four shells—(A) 0.25, (B) 0.2, (C) 0.05, (D) 0.025; length of the spines 0.12.

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

2. Staurocromyum quadrispinum, n. sp.

Radial proportion of the four spheres = 1 : 3 : 9 : 12. Both medullary shells with small, regular, circular pores. Both cortical shells with irregular, roundish pores. Surface covered with short, conical by-spines. Four main spines cylindro-conical, somewhat longer than the shell diameter.

Dimensions.—Diameter of the four shells—(A) 0.24, (B) 0.18, (C) 0.06, (D) 0.02.

Habitat.—Central Pacific, Station 265, depth 2900 fathoms.

Definition.— with four concentric lattice-spheres and four crossed, equal, branched spines.