Habitat.—Indian Ocean, surface, Cocos Islands (Rabbe).
8. Larnacantha prismatica, n. sp. (Pl. [50], fig. 6).
Cortical shell smooth, four-sided prismatic, with eight short, parallel, three-sided pyramidal spines; these lie opposite in pairs in four parallel longitudinal lines, as prolongations of the four lateral edges of the prism, and arise from its eight corners. Pores regular, circular, three times as broad as the bars; about fourteen on the half meridian. Proportion of the three axes = 2 : 3 : 4. Medullary shell half as long as the cortical shell.
Dimensions.—Length of the cortical shell 0.11, breadth 0.07, height 0.05; pores 0.006, bars 0.002; length of the medullary shell 0.06.
Habitat.—Pacific, central area, Station 263, depth 2650 fathoms.
9. Larnacantha decacantha, n. sp.
Cortical shell thorny, with ten short and stout, conical, radial spines, two opposite on the poles of the principal axis (as prolongations of inner axial beams), eight others opposite in pairs in two crossed diagonal planes. Pores irregular, roundish, twice to four times as broad as the bars; about sixteen on the half meridian. Proportion of the three axes = 3 : 3.75 : 4. Medullary shell about one-third as long as the cortical shell.
Dimensions.—Length of the cortical shell 0.16, breadth 0.15, height 0.12; pores 0.008 to 0.016, bars 0.004; length of the medullary shell 0.06.
Habitat.—North Atlantic, Station 354, surface.
10. Larnacantha dodecantha, n. sp.