Animals having ribs or processes, or short, slight, and free vertebræ, forming a series of separate centrums, deeply cupped at both ends, one of which is converted by ossification in the mature animal into a ball, which may be the front one, as in the Surinam Toad, Pipa, or the hind ones in the Frogs and Toads, Rana. The skin is nude, limbs digitate, gills embryonal,—permanent in some, in most lost in metamorphosis,—to be succeeded by pulmonary respiration,—or both; a heart with one ventricle and two auricles. They consist of:—
| I. Ophiomorpha. | |
|---|---|
| Cæciliadæ or Ophiosomæ. | |
| II. Icthyomorpha. | |
| Proteidæ or Sirens, Proteus, Newts, and Salamanders. | |
| III. Theriomorpha. | |
| Aglosa | Pipa or Surinam Toads. |
| Ranidæ | Frogs. |
| Hylidæ | Tree Frogs. |
| Bufonidæ | Toads. |
Chelonia, or Turtles.
Distinguished by the double shield in which their bodies are enclosed, whether they are terrestrial, fresh-water, or marine.
| The Turtles, Chelonia, have the limbs natatory. | ||
| Mud Turtles, Trionyx, | } limbs amphibious. | |
| Terrapens, Emys, | ||
| Tortoises, Testudo, limbs terrestrial. | ||
Lacertilia.
Having a single transverse process on each side, single-headed ribs, two external nostrils, eyes with movable lids; body covered with horny, sometimes bony, scales.
Lacerta—the Monitors, Crocodiles, Lizards; having ambulatory limbs.
Anguis—Ophisaurus, Bimanus, Chalcides, Seps; limbs abortive; no sacrum.
Ophidia.
Having numerous vertebræ with single-headed hollow ribs, no visible limbs, eyelids covered by an immovable transparent lid; body covered by horny scales. It includes:—