[Fr., from L. repere, to creep.] Reptiles form the first class of the higher vertebrata, or of those which never breathe by gills, like the amphibians. Their blood is cold, and they closely resemble birds in the development of their young; but their eggs are very large. Reptiles include alligators, turtles, snakes, and lizards. Formerly amphibians were classed with reptiles, and are still properly called reptiles, though more closely allied to the fishes. Reptiles, except tortoises, are long, often nearly cylindrical, and usually covered with scales, and have long tails. The feet are of different lengths, but seldom suffice to support the body, the belly trailing on the ground when the animal is in motion. The mouth is large and armed with sharp, hooked teeth ; but in tortoises no teeth exist. The heart generally has two auricles and one ventricle. The ribs are always well developed; the limbs when present are well developed; the feet are freely movable, and end in strong claws. Except tortoises, all reptiles are carnivorous, feeding upon living prey; their teeth not being constructed for the division of flesh, they swallow their victims whole. Reptiles are essentially inhabitants of the warmer regions of the earth. In earlier geological periods, before the age of the mammalia, reptiles were often quadrupeds of immense size and strength. Some were essentially tripeds, supporting themselves on their hind legs and tails; and some gained the habit of flying, with the aid of membraneous wings.
THE AGE OF REPTILES..