ALLIGATOR, an animal so closely allied to the crocodile that the old naturalists classed them together as forming one genus. In popular speech the two are often confused (see CROCO DILE). It differs from the true crocodile principally in having the head broader and shorter, and the snout more obtuse; in having the fourth, enlarged tooth of the under jaw received, not into an external notch, but into a pit formed for it within the upper one; in wanting a jagged fringe which appears on the hind legs and feet of the crocodile ; and in having the toes of the hind feet webbed not more than half way to the tips. Two species, A. mississippiensis in the southern states of North America up to 12ft. in length, and the small A. sinensis in the Yang-tse-kiang, are still living. In Central and South America alligators are repre sented by five species of the genus Caiman, which differs from Alligator by the absence of a bony septum between the nostrils, and by the fact that the overlapping bony scales of the ventral armour are each composed of two bones. C. niger of the Amazon grows to a length of 2of t.