REPTILIA, reptiles; cold-blooded, oviparous, or ovoviviparous, vertebrate animals having the skin covered with scales or scutes; heart with two auricles, ventricular chamber incompletely di vided. Respiration takes place by lungs, respiratory movements being slow and irregular. Intestinal tract and urogen ital organs open into a common cloaca. Aristotle was the first naturalist who wrote on reptiles. Some progress in classification was made by Ray (1628 1705) and Linnmus (1707-1778). Brongniart, in 1799, first recognized the characteristics by which the Batrachia differ from other reptiles and form a natural passage to the fishes. In 1863 in his Hunterian Lectures, Huxley adopted the term Sauroids for that di vision of the vertebrates which he after ward called Sauropsida. He divides the Reptilia into the following orders: Che Plesiosauria, Lacertilia, Ophidia, Ichthyosauria, Crocodilia, Dicynodontia, Ornithoscelida, and Pterosauria. Owen makes reptiles proper the highest of the five sub-classes into which he finally di vided his Hmmatocrya with orders: Ichthyopterygia (extinct), Sattropterygia (ex tinct), Anontodontia (extinct), Chelonia, Lacer tilla (with the extinct Mosasaunts), Ophidia, Croco dilia (with the extinct Teleosaterus and Strepsos pendylys), Dinosayria (extinct), and Pterosauria (extinct).
Professor Mivart divides the Reptilia into the following orders: Ichthyopterygta (extinct), Anomodontia (ex tinct), Dinosauria (extinct), Ornithosauria (ex tinct), Crocoditia, Ithynchocephatia, Sauroptery gia, Lacertilia, Ophidia, and Chelonia.
The first appearance of reptiles is be lieved to be indicated by remains of a marine Saurian (Eosaurus acadianus) of Carboniferous age. Proterosaurus is found in the Permian. In Mesozoic times the reptilian type appears in such variety and in such a high state of development that this era has been distinguished as the Reptilian Age. In the Trias large marine Saurians and Dinosaurs are met with; more gigantic forms were developed in the Jurassic period; and the class at tained its highest culmination in the Chalk.