Crab

Crabs are decapod crustaceans of the infraorder Brachyura, which typically have a very short projecting tail usually entirely hidden under the thorax. They live in all the worlds oceans, in fresh water, and on land, are generally covered with a thick exoskeleton and have a single pair of claws. Many other animals with similar names such as hermit crabs, king crabs, porcelain crabs, horseshoe crabs and crab lice are not true crabs.