BATRACHIA CONSIDERED AS A CLASS. 



237 



Batrachians have the skull very flat and usually broad, 

 and of a very open structure ; two occipital condyles for 



FIG. 269. 



Skeleton of a Batrachian Frog. 



the articulation of the head with the body ; and the ribs 

 very short or wanting. 



The young batrachians breathe by means of gills, and, 

 in most cases, live in the water, being thus more or less 

 fish-like, and are called tadpoles. But in the adult state, 

 with few exceptions, the gills disappear and then these 

 animals breathe by means of lungs. Their lungs are two 

 and equal, and their heart has never more than three 

 cavities two auricles and one ventricle. 



The Batrachia comprise the following Orders : 



1. ANOURA or Tailless Batrachians, as Frogs and Toads. 



2. URODELA or Tailed Batrachians, as Salamanders, Tritons, Si- 



rens, etc. 



3. APODA or Footless Batrachians, as snake-like batrachians or 



Csecilians. 



