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Orver IV. BATRACHIA. Brogniart. 
The many and great differences that exist between this and the three preceding 
orders of reptiles, have led several excellent herpetologists of our day to arrange 
the animals it includes as a distinct class, named Amphibia; as they are in fact, 
at one time, animals that live in water, and respire by means of gills, like fishes, 
and at another they breathe atmospheric air with lungs, like mammalia. 
CHARACTERS. 
1. The body is depressed, round, or elongated, and with or without a tail; the 
skin is soft, naked, or without a shell, and most commonly without apparent 
scales, (ceecilia.) 
2. The extremities vary in number and proportion, or are entirely wanting. The 
fingers and toes are destitute of nails, and are rarely provided with a horny 
sheath, (Datylethra.) 
3. There is no neck distinct from the body, and the head is joined to the vertebra 
by two condyles. 
4. There are in general three movable eyelids, and no visible external meatus of 
the ear, though the tympanum is often very distinct. 
5. The sternum is distinct in most species, but is never joined to the ribs, which 
are either very short or entirely wanting. 
