Page:Natural History, Reptiles.djvu/15

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The Mailed or true Reptiles are principally distinguished by having the body encased in a series of plates of various degrees of hardness, sometimes imbedded, like stones in a pavement, into compact shields, at others forming overlapping scales, and yet again constituting a granular or tuberculous shagreen. In many particulars their anatomical organization is of a higher grade than that of the Amphibia; they have perfect ribs; and the occipital condyle, or joint by which the skull is connected with the spinal column, is single. They are subject to no metamorphosis, but are evolved from the egg in the form of the parents: gills (branchiæ) are never present in any stage, but respiration is performed entirely by means of lungs. The economy of. reproduction partakes of the characters of that of Mammalia and Birds, and not that of Fishes; the eggs are always furnished with a calcareous covering, either shelly or coriaceous in texture.

The Enoplia are divided into four Orders, founded on diversities of form, the presence or absence of limbs, and the character of the mailed covering. These are named Testudinata, Loricata, Sauria, and Ophidia.