\Am*phib"i*a\, n. pl. [See {Amphibium}.] (Zo["o]l.)
One of the classes of vertebrates.
Note: The Amphibia are distinguished by having usually no
      scales, by having eggs and embryos similar to those of
      fishes, and by undergoing a complete metamorphosis, the
      young having gills. There are three living orders: (1)
      The tailless, as the frogs ({Anura}); (2) The tailed
      ({Urodela}), as the salamanders, and the siren group
      ({Sirenoidea}), which retain the gills of the young
      state (hence called {Perennibranchiata}) through the
      adult state, among which are the siren, proteus, etc.;
      (3) The C[oe]cilians, or serpentlike Amphibia
      ({Ophiomorpha} or {Gymnophiona}), with minute scales
      and without limbs. The extinct Labyrinthodonts also
      belonged to this class. The term is sometimes loosely
      applied to both reptiles and amphibians collectively.