Shell oval, conoidal, ribbed. There are 14 to 22 rounded, roughened radiate ribs, a few of them short, crossed by incremental ridges. Colour white, nearly always obscured by a layer of Nulliporites. Apex a little in front of the middle, obtuse ; slopes straight; margin denticulate. Inside bluish-white, spatula white or brown, sometimes faintly radiately streaked with black ; margin with a black border or dark-brown spots. Length, 14 mm. ; breadth, 13 mm. ; height, 9 mm. (type). Length, 13 mm. ; breadth, 9-5 mm. ; height, 5 mm.

New Zealand. The type is from Dunedin ; North and South Islands ; Chatham Islands.