Shell of moderate size, 35.6 mm. (1,375 inches) in length, ovate, with irregularly corrugated margins, depressed, with the apex varying between subcentral and the anterior third. Sculpture rather coarse and irregular, of rounded radial ribs, 14 or 15 of them of primary strength, and these project at the margins, slightly more than do the corrugations between them. The whole surface is crossed by dense crisp sublamellose concentric lirae. Colour of exterior greenish black, with an elongated white streak towards the margin upon most of the primary radials; interior dark silvery grey, with the spatula dark olive-brown, clouded in part by a bluish white callus. The marginal white streaks of the exterior show through strongly upon the inner surface. Length: 27-36 mm; Width 21-28 mm; Height: 7-8,5 mm)

This species is easily recognised by its dark silvery grey to greenish black colour, relieved by short marginal white streaks at the extremities of the primary radials. Apparently the species is restricted in habitat to dark volcanic rock. The relationship is with the radiata series, but the shell is sufficiently distinct, particularly in sculpture, to discount the possibility of it being merely an ecotype.

Central Pacific: Samoa and New Hebrides.