BATRACHIANS. 185 



13atrarf)ta. 



(The Batrachians.) 



Cold-blooded Vertebrates, allied to the fishes, but 

 differing in several respects, notably in the absence of 

 rayed fins, the limbg being usually developed and func- 

 tional, with the skeletal elements of the limbs of 

 Reptiles; toes usually without claws. 



The Batrachians undergo a more or less complete 

 metamorphosis; the young ("tadpoles") being aquatic 

 and fish -like, breathing by means of external gills or 

 branchiae; later in life, lungs are developed and (except- 

 ing in Proteida) the gills disappear. Skin naked and 

 moist (rarely having imbedded scales) and used to some 

 extent as an organ of respiration. Heart with two 

 auricles and a single ventricle. 



Reproduction by means of eggs which are of com- 

 paratively small size, without hard shell, developed in 

 water or in moist situations. 



The Batrachians diifer more from the Fishes in 

 appearance than in reality, and they are sometimes 

 combined into one group (Ichthyopsida), the Birds and 

 Reptiles constituting another (Sauropsidd). 



ORDERS OF BATRACHIA. 



* Body short, depressed ; tail wanting in the adult; four dereloped 



limbs, ihe posterior being much enlarged. . AMTTRA, W. 



** Body lengthened, with a distinct tail ; hind limbs if present 



not specially elongated. 



f With no external gills or branchiae when adult; eyelids 

 present URODELA, X. 



