Page:Scientific results HMS Challenger vol 18 part 1.djvu/1037

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Definition.—Plates of the shell not dimply, without prominent crests.

1. Acontaspis lanceolata, n. sp.

Shell thin walled, even, without crests and dimples between them, perforated by about three hundred pores of different sizes: forty aspinal pores elliptical, about as large as the irregular (fifty to sixty) sutural pores, and two to four times as broad as the small circular coronal pores (eight to twelve being on each plate, altogether about two hundred). Between the pores numerous short conical by-spines. Radial main spines lanceolate, about as long as the radius. (Similar to Coscinaspis peripora, Pl. 138, fig. 1, but with broad lanceolate spines and numerous short by-spines.)

Dimensions.—Diameter of the shell 0.15, aspinal and sutural pores 0.012 to 0.015, coronal pores 0.004 to 0.008.

Habitat.—South Atlantic, Station 325, surface.

Definition.—Surface of the shell dimply, with a network of prominent crests.

2. Acontaspis hastata, n. sp. (Pl. 134, fig. 16).

Shell thick walled, with numerous (one hundred and seventy to one hundred and ninety) dimples, which are separated by an elevated network of prominent crests. In the centre of each plate a larger dimple with a couple of aspinal pores, surrounded by a corona of ten or twelve smaller dimples, each of which contains a single pore (a coronal and sutural alternately). All pores circular or roundish, nearly of the same size. If the shell be quite regularly developed, there are fifty to sixty sutural pores and one hundred to one hundred and ten coronal pores (six in each equatorial plate, five in each of the other plates). The knobs of the meeting crests are conical, and bear each a simple short by-spine. Radial main spines compressed, at the distal end spear-shaped, with a rhomboidal plate below the apex, about as long as the radius.

Dimensions.—Diameter of the shell 0.18, of the pores and bars 0.01.

Habitat.—Western Tropical Pacific (off the Philippines), Station 215.

3. Acontaspis furcata, n. sp.

Shell thick walled, dimply, with a network of crests, of the same composition as in the foregoing species, with one hundred and seventy to one hundred and ninety dimples (twenty aspinal, one hundred to one hundred and ten coronal and fifty to sixty sutural dimples). All dimples and pores nearly of the same size. Each node of the crested network bears a stout by-spine, which is forked