True crabs are mainly cancer, carcinus, portumus etc. Crabs reach the highest degree of cephalization among crustaceans. They remain buried among rocks and mud in shallow water. The cephalothorax is broader than longer, flat and disc-like. Both the pairs of feelers are small. The antennules and the eye stalks are contained in sockets of the carapace. The third maxillipedes are flat and plate like and cover the other mouth parts. Five pairs of trhoracic legs are well developed and clawed. The first legs are chelate forming the large pinching claws; remaining legs are non-chelate, but stout.
Abdomen is very short, with uncalcified, soft sterna region. It is segmented some what triangular and thin. It is permanently bent under the cephalothorax, fitting into a groove in the thoracic sterna, thus remaining almost invisible in dorsal view of the animal. Abdomen is narrower in male but some what broader in female.
Crabs form an important diet of man with great nutritive value. The most edible portions are their tails (abdomen) almost all of which are composed of muscles. The flexor muscles are particularly bulky. There is also some good meat in their chelipeds. In mud crabs the claws are the best part of the animal to eat. The muscles are eaten freshly cooked or canned. The blue crab (callinecters) is held captive until it molts, then sold in the soft-shelled condition, after removal of viscera the whole animal is cooked and eaten.