Shell rather thick and large (attaining 30 cm in length), subcircular in outline, with a short and ill-defined posterior ear which is not drawn out into a wing-like process. Anterior margin markedly protruding beyond the tip of anterior ear. Outer surface of valves, when not worn, covered with flattened, imbricating concentric scales bearing large and irregular, flat spines with blunt ends, roughly arranged in radial rows and projecting at shell margins. Hinge completely devoid of teeth. Colour: outside of shell uniformly fawn, sometimes with radial stripes of darker spots in umbonal region; then, ground colour in that region green, dark brown, or purple. Internal nacreous area highly lustrous, silvery with a variably extended golden border. Non-nacreous margin clear, of plain horny colour.
