American crocodile

The epidermal exoskeleton of the alligator consists of oblong horny scales, arranged in transverse rows; the long axes of the scales are parallel to that of the body. On the tail, except along the mid-dorsal line, and on the ventral side of the trunk and head these scales are very regular in outline and arrangement; on the sides of the head and trunk and on the legs they are much smaller and less regularly arranged, while along the mid-dorsal line of the tail, especially in its posterior half, they are elevated into tall keels that give the tail a large surface area for swimming. The first three digits of both manus (fore foot) and pes (hind foot) are armed with horny claws, which also belong to the epidermal part of the exoskeleton.