2. Stylocyclia prionacantha, n. sp. (Pl. [37], fig. 6).
Phacoid shell two and a half times as broad as the medullary shell, surrounded by five to six chambered rings, which are divided by fifty to sixty piercing radial beams into square chambers. Pores in the thick-walled phacoid shell regularly circular, increasing in size from the centre; eight to nine on its radius. Pores on the surface of the chambered girdle smaller, very irregular, two to three on each ring. Both marginal spines longer than the diameter of the disk, with broad serrated edges.
Dimensions.—Diameter of the disk (with five rings) 0.23, of the phacoid shell 0.12, of the medullary 0.05.
Habitat.—Pacific, central area, Station 268, depth 2900 fathoms.
3. Stylocyclia excavata, n. sp. (Pl. [37], fig. 8).
Phacoid shell four times as broad as the medullary shell, surrounded by four chambered rings, which are divided by twenty to thirty radial beams into broad chambers. The height of the rings increases strongly from the centre, so that the fourth ring is two and a half times as high as the first. Pores irregular, roundish; five to six on the radius of the phacoid shell, one to two on the breadth of each ring. Margin of the disk smooth. Both marginal spines thin and long, cylindrical, arising from the medullary shell, longer than the diameter of the disk.
Dimensions.—Diameter of the disk (with four rings) 0.25, of the phacoid shell 0.1, of the medullary shell 0.025.
Habitat.—Fossil in the rocks of Barbados. Indian Ocean, Cocos Islands, Rabbe.
4. Stylocyclia amphacantha, n. sp.
Phacoid shell twice as broad as the medullary shell, surrounded by five chambered rings, divided by piercing beams each into forty to fifty chambers. Pores regular, circular; eight to nine on the radius of the phacoid shell, one on each chamber. Margin of the disk thorny. Both marginal spines strong, conical, as long as its radius.