Atlantic rock oyster. A variety of oyster up to 15 cm (6") in length found on the American side of the Atlantic. Unlike many oysters this is usually cooked, served on the half shell. This is because it is quite a fatty oyster, particularly when large, which is improved by cooking. All down the eastern seaboard the Atlantic oyster is called after the area in which it is found, e.g. the Long Island oyster, Chesapeake Bay oysters and so on. The best known is probably the bluepoint.