Reptiles

Reptiles, a class of Vertebrate Animals, below the Birds and above the Amphibians, but with affinities to both. The body is covered with horny scales or bony plates or shields; the temperature of the body does not greatly exceed that of the medium in which the animals live; the heart in most is three-chambered, only the alligators and crocodiles having two ventricles. Respiration is carried on by lungs, never by gills. The skull articulates with the atlas vertebra by means of a single condyle, and the jawbone with the skull by means of the quadrate bone. Most of the class lay eggs, but in some - the viper, for example - the eggs are hatched within the body of the mother. There are five living orders: (1) Chelonia, (2) Rhvnchocephalia, (3) Lacertilia, (4) Ophidia, and (5-) Crocodilia, for which see respectively Tortoises, Sphenodon, Lizards, Snakes, and Alligators and Crocodiles.