Tuatua

Paphies subtriangulata is a species of edible bivalve clam known as tuatua in the Māori language, a member of the family Mesodesmatidae and endemic to New Zealand. It is found on all three of the main New Zealand islands, buried in fine clean sand on ocean beaches. The large shell is asymmetrical, with the hinge at one side. Its closest relative, the pipi , has a symmetrical shell.

Source: Wikipedia