Shell thin, medium, variable in shape, roughly rounded, ovate to elongate-ovate, inequivalve, cardinal area well-developed. Valve exterior with low radial undulations forming a series of rather broad ribs bearing short flattened spines. Interstices of the main ribs broad and radially ridged. Crenulations of internal margins correspond with the outer radial sculpture; 8-12 spinose ribs on right valves, and 5-8 on left valve. Bifid hinge teeth on right valve. Umbones irregular. Colour: exterior white to cream with a few purple to blackish-brown