Also known as ocean quahogs, these hard-shell clams live in the North Atlantic, especially around Maine. They are distinct from northern and southern quahogs in that they have dark brown or black round shells and live deeper in the ocean. They have a slower life cycle than other clams, taking about six years to reach maturity, and they can live to be hundreds of years old. Mahogany clams have a stronger flavor than quahogs and are particularly suited to pasta dishes.