Page:Scientific results HMS Challenger vol 18 part 1.djvu/466

258 3. Echinomma aculeatum, Haeckel.

Actinomma aculeatum, Stöhr, 1880 Palæontogr., vol. xxvi. p. 92, Taf. ii. fig. 11.

Cortical shell thick walled with regular circular pores, of the same breadth as the bars; eight to ten on the radius. Radial proportion of the three spheres = 1 : 2 : 8. Surface covered with short conical by-spines about twenty strong main spines, three-sided pyramidal, one-third as long as the shell diameter.

Dimensions.—Diameter of the outer shell 0.16, middle 0.04, inner 0.02; cortical pores and bars 0.003; length of the main spines 0.05, basal breadth 0.013.

Habitat.—Fossil in the Tertiary rocks of Sicily and Barbados; living in the Atlantic, Station 332, depth 2200 fathoms.

4. Echinomma diadema, n. sp.

Cortical shell thick walled with regular circular pores, twice as broad as the bars; sixteen to eighteen on the radius. Radial proportion of the three spheres = 1 : 3 : 11. Surface covered with short bristle-shaped by-spines one third as long as the twelve stout conical main spines, which reach in length the radius, and lie opposite in pairs in six axes.

Dimensions.—Diameter of the outer shell 0.22, middle 0.06, inner 0.02; cortical pores 0.006, bars 0.003 length of the main spines 0.12, basal breadth 0.02.

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

Definition.—Pores of the cortical shell irregular, of different size or form.

5. Echinomma sphærechinus, n. sp. (Pl. 29, fig. 2).

Actinomma sphærechinus, Haeckel, 1879, Atlas (pl. xxix. fig. 2).

Cortical shell thin walled, with irregular, roundish pores, twice to five times as broad as the bars; five to seven on the radius. Both medullary shells with regular, circular pores, twice as broad as the bars. Radial proportion of the three spheres = 1 : 2 : 4. Surface covered with thirty to fifty pyramidal main spines, as long as the diameter of the inner shell, and with numerous small conical by-spines of half the length.

Dimensions.—Diameter of the outer shell 0.11, middle 0.05, inner 0.025; cortical pores 0.01 to 0.02, bars 0.004; length of the main spines 0.03, basal breadth 0.005.

Habitat.—North Atlantic, Station 353, surface.

6. Echinomma trinacrium, Haeckel.

Actinomma trinacrium, Haeckel, 1862, Monogr. d. Radiol., p. 441, Taf. xxiv. figs. 6-8.

Cortical shell thin walled, with irregular, roundish pores, twice to three times as broad as the bars. Both medullary shells with regular, circular pores. Radial proportion of the three spheres