Limpet. A conical, univalve shellfish. These they may be cooked by washing them and then boiling them for about 5 minutes in seawater (or heavily salted water) is recommended. They have a small amount of meat and it is inclined to toughness, like a lot of those things that cling onto rocks. Alternatively the meats can be dug out and used in fish stews or chowders or in sauces to garnish other fish.