Broadly trigonal, compressed, thin-walled, dark brown, with 15-25 coarse radial ridges adorned with inrolled spines; interior glossy black-brown, with central muscle scar at or protruding above upper margin of internal nacreous border, mantle golden orange. North Carolina to Florida, Bermuda, Bahamas, West Indies, Gulf of Mexico, Caribbean Central America, South America (Venezuela). Length 90 mm (to 355 mm). Compare Atrina seminuda, which has a beige or pale yellow mantle and a muscle scar well within the inner nacreous layer.