High Quality Content by WIKIPEDIA articles! The velvet crab (alternatively velvet swimming crab or devil crab), Necora puber, is a species of crab. It is the largest swimming crab (family Portunidae) found in British coastal waters, with a carapace width of up to 100 millimetres (3.9 in), and the only species in the genus Necora. The body is coated with short hairs, giving the animal a velvety texture, hence the common name. It is one of the major crab species for United Kingdom fisheries.