The hard clam (Mercenaria mercenaria), also known as a quahog (or quahaug), round clam, or hard-shell (or hard-shelled) clam, is an edible marine bivalve mollusk that is native to the eastern shores of North America and Central America, from Prince Edward Island to the Yucatán Peninsula. It is one of many unrelated edible bivalves that in the United States are frequently referred to simply as clams, as in the expression "clam digging". Older literature sources may use the systematic name Venus mercenaria; this species is in the family Veneridae, the venus clams.Confusingly, the "ocean quahog" is a different species, Arctica islandica, which, although superficially similar in shape, is in a different family of bivalves: it is rounder than the hard clam, usually has black periostracum, and there is no pallial sinus in the interior of the shell. They have been known to live up to 500 years. In 2006 a Quahog clam was taken from the ocean floor at the north coast of Iceland. It was later confirmed to be 507 years old and is recognized as the world's longest lived non-colonial animal.