Amphibia, a term used by Linnaeus to include reptiles, the modern class Amphibia, and some fishes; Cuvier adopted the term, but reduced the group by leaving out the fishes. It is now taken to include animals between the class Pisces (fishes) on the one hand, and the class Reptilia (reptiles) on the other, and was united by Huxley with the former class in his division Ichthyopsida (q.v.). The amphibia include four orders: Urodela (newts and salamanders), Anura (frogs and toads), Peromela (limbless snake-like forms), and the extinct Labyrinthodonta. The Amphibian embryo is never furnished with an amnion, and the urinary bladder is the only representative of the allantois; gills are developed and persist for a longer or shorter period; but true lungs are always found in the adult. The limbs when present are arranged as in the higher vertebrates, and terminate typically in five digits; when median fins occur they are never furnished with fin-rays.