Geukensia granosissima

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Geukensia granosissima, commonly known as the southern ribbed mussel, is a saltwater mussel and a marine bivalve in the mussel family (Mytilidae). It lives along the Atlantic coast of North America, especially in the Florida Keys, the Caribbean, and the Gulf of Mexico. A closely related species, Geukensia demissa, is found farther north on the same coast. The shells can reach about 10 cm in length.