Callinectes is a genus of crabs, including the blue crab, C. sapidus. Members of the genus Callinectes have a pair of flat rear legs (pereiopods) shaped like oars. Callinectes species also have a flat, broad carapace with a series of distinct teeth along the front, around the eyes and terminal spines. The largest teeth are the "frontal teeth," between four and six teeth located between the eyes. Crabs in this genus are characteristically olive-green or blue on the back and white underneath, with blue or red areas covering the relatively small claws. Some species vary in claw size, spines and colouration.