Page:Scientific results HMS Challenger vol 18 part 1.djvu/372

164 1. Stauracontium cruciferum, n. sp.

Cortical shell thin walled, smooth, with regular, hexagonal pores, four times as broad as the bars; eight to ten on the quadrant. Radial proportion of the three spheres = 1 : 3 : 9. Connecting radial beams between them six (opposite in pairs in the three dimensive axes), but only four of them are prolonged outside into four stout three-sided prismatic spines, lying in one equatorial plane, as long as the shell diameter.

Dimensions.—Diameter of the outer shell 0.22, middle 0.07, inner 0.025; cortical pores 0.012, bars 0.003; length of the spines 0.2.

Habitat.—Central Pacific, Station 268, depth 2900 fathoms.

2. Stauracontium tetracanthum, Haeckel.

Haliomma tetracanthum, Ehrenberg, 1872, Abhandl. d. k. Akad. d. Wiss. Berlin, p. 295, Taf. x. figs. 7, 8.

Cortical shell thin walled, smooth, with regular, circular pores, three times as broad as the bars; five to six on the quadrant. Radial proportion of the three spheres = 1 : 3 : 12. Radial spines three-sided pyramidal, about as long as the shell diameter.

Dimensions.—Diameter of the outer shell 0.12, middle 0.03, inner 0.01; cortical pores 0.01, bars 0.003; length of the spines 0.1.

Habitat.—Indian Ocean, Zanzibar, depth 2200 fathoms, Pullen.

3. Stauracontium tetracontium, Haeckel.

Actinomma tetracanthum, Stöhr, 1880, Palæontogr. 26, p. 91, Taf. ii. fig. 6.

Cortical shell thin walled, rough, with regular, circular pores, of the same breadth as the bars; six to seven on the quadrant. Radial proportion of the three spheres = 1 : 2.5 : 8. Radial spines three-sided pyramidal, nearly as long as the shell diameter.

Dimensions.—Diameter of the outer shell 0.1, middle 0.03, inner 0.013; cortical pores and bars 0.006; length of the spines 0.08.

Habitat.—Fossil in Tertiary rocks of Sicily; Grotte, Caltanisetta.

Definition.—Pores of the cortical shell regular, and of nearly equal size and similar form; surface covered with numerous small thorns or by-spines.

4. Stauracontium daturæforme, Haeckel.

Actinomma daturæforme, Stöhr, 1880, Palæontogr. 26, p. 93, Taf. ii. fig. 13.

Cortical shell thick walled, covered with short thorns, and with regular, hexagonal pores, five times as broad as the bars; six to seven on the quadrant. Radial proportion of the three spheres = 1 : 3 : 3.5. Radial spines six-sided pyramidal, about half as long as the radius and one-fourth as broad.