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Sauria or true Lizards, resemble the Crocodiles in their external form, the body being lengthened and tapering to the tail, which is likewise long, in the possession of four limbs (at least in most cases), and in the presence of numerous teeth. They have a moderate number of perfect and moveable ribs, capable of being raised for the purpose of respiration. The lung extends more or less towards the hind part of the body, often penetrating into the abdomen. Their skin is covered with scales, which in many overlap at the hinder edges; in others are flat, with the edges in common contact, and in some are so minute as to impart a kind of granulated or shagreened surface. "The eyes are furnished with eyelids; the ear in some protected by a simple valve, in others by scales rather larger than the surrounding ones, and in others the tympanum is on a level with the surface of the skin."

The ordinary mode of reproduction is by eggs, which are coated with a calcareous, brittle shell: those of the Chameleon, however, have the covering tough, resembling parchment. In the extensive Family of the Skinks, all the species, as we believe, are ovoviviparous, as are also some of the Lizards proper, for example, our own little Zootoca. The young come into existence in the same form which they retain through life.