Burrowing deeply within coral in shallow water, the upper profile is flat and nearly flush with the reef.  The fleshy mantle typically obscures the shell unless alarmed.  Color pattern extremely variable, often with broken lines of black eye spots near mantle margins.  The incurrent siphonal opening is lined by y-shaped frills.  The smallest giant clam, attaining only 6 inches.  Andaman Sea to Okinawa, Caroline Islands and Fiji.