Shell of moderate size, 30 to 71 mm. in length, broadly ovate and of low to moderate height, with the apex at about the anterior third, sculptured with numerous low rounded radial ridges, crossed by dense delicate concentric growth lamellae; margin weakly scalloped. Colour, externally dark reddish brown, mostly showing a white or pale yellowish star at the apex, this often persisting to the adult stage, and occasionally with long rays extending from the points of the star right to the margin; interior bluish or purplish grey with a silvery sheen, the star pattern usually showing through; spatula ill-defined, a chestnut smeer often clouded by a whitish callus. Length 33-71mm; Width 26-58 mm; Height: 10-19 mm.

Shell depressed oval, reddish or black, with granular ribs. Sculptured by numerous radiate ribs, of which about 10 to 20 are more elevated than the others ; all the ribs are cut up into granules by strong concentric furrows. Sometimes the ribs are more equal, but the concentric sculpture is always prominent. Colour usually reddish, but often black, brown, or cinereous; there are white rays at the apex, forming a star, but they frequently extend to the margin, and sometimes they are altogether absent. Apex at the anterior third or fourth. Interior white, cinereous or greyish-brown, showing all the white star-shaped rays ; iridescent in fresh specimens ; central area not well defined, chestnut-brown. Length, 25 mm. ; breadth, 19 mm. ; height, 7 mm. Length, 32 mm. ; breadth, 27 mm. ; height, 11 mm.
Hab.—Cape Maria van Diemen ; Bay of Islands (J. C. Anderson) ; Lyall Bay to Island Bay, Cook Strait; Queen Charlotte Sound, in 6 fathoms (Captain Bollons) ; Nelson ; New Brighton ; Campbell Island, on rocks (Captain Bollons). Brought to England by Captain Cook.

This species lives at and just below low tide on smooth rock faces in clean water situations but is not generally common. It is easily recognised by its reddish brown external colour, bluish silvery interior, and usual presence of an apical star in paler colour. It is more abundant in the northern part of its range.

New Zealand; North, South and Stewart Islands.