Shell of a giant clam (Tridacna gigas) which has died. Tridacna gigas is one of the many species of clams belonging to the genus Tridacna. They are the largest living bivalve mollusks known and live in warm and shallow marine environments amidst coral reefs. They are a delicacy, and threatened by over-fishing. Photographed off the coast of Arborek, Indonesia.