Larkinia grandis is a genus of saltwater clams in the family Arcidae, the ark clams.
Shell of Larkinia grandis can reach a diameter of about 7.5 centimetres (3.0 in) and a height of about 9.6 centimetres (3.8 in). These shells are white, with 26 ribs and a dark, smooth periostracum.
This species is present in the North Pacific Ocean (Mexico, El Salvador, Peru, Gulf of California).
