Marine bivalve mollusc. Asymmetric valves, the upper valve is flat and red-brown coloured, and the lower valve is convex and white or yellowish coloured, with concentric or zig-zag brown spots, both valves with two "ears", one on each side of umbo or central point. Very pronounced radial ribs. Internally valves are pearly white with brown spots by the edge. It can measure up to 17 cm in diameter.