Several species of crabs are found in the waters of India, but only a few are used as food. Some of the species of crabs are highly nutritious and as delicious as prawns. The crabs of India reach the highest degree of specialization. These are found buried among the rocks are mud in the shallow waters.

The cephalothorax is broader than longer, flat and disc-like both the pairs of feelers are small. The antennules and the eyestalks are contained in sockets of the carapace. The third maxillipeds are flat and plate-like and cover the other mouthparts. The five pairs of thoracic legs are well developed and clawed. The first legs are clelate, forming the large pinching claws; the remaining legs are non-clelate but shout.

The abdomen is very short with an uncalcified, soft stemal region. It is segmented, somewhat triangular and thin. It is permanently bent under the cephalothorax, fitting into a groove in the thoracic sterna, thus remaining almost invisible in the dorsal view of the animal. The abdomen is narrow in male but some- what broader in female. The pleopods are greatly reduced, the male retaining only two pairs of them, which serves as copulatory organs, the female has four pairs of carrying the eggs. The uropods are usually absent.

During copulation, the female lies beneath the male or the reverse position so that their ventral surfaces are in contact. Pleopods of first-pair, which conduct the sperms, are inserted into the opening of the female. The newly layed eggs from a bright organs mass, sometimes called a sponge. The young hatches in the zoaca stage, which passes through a postlaryal megalopa stage before reaching maturity.