xxr ] CLASSIFICATION 561 



these, limbless forms are also known, and there seems to be some 

 probability that these were the ancestors of the Gymnophiona. 

 Hence within this ancient group the beginnings of the division of 

 the Amphibia into the three orders by which it is now represented 

 had already shown themselves. 



The ckss of recent Amphibia is divided as follows : 



Order I. Urodela. 

 Amphibia retaining throughout life a long tail. 



Sub- order 1. Ichthyoidea. Urodela retaining throughout 

 life external gills or gill-slits or both. 



Family (1) Amphiumidae. 



Both the upper and lower jaws are furnished with teeth. 

 Fore- and hind-limbs small. Eyes small and devoid of lids. 

 The gill-slits are in a vanishing state, and the gills disappear in 

 the adult. 



Ex. Amphiuma, Cryptobranchus japonicus, C. (Menopoma) 

 alleghaniensis (the Hell-bender). 



Family (2) Proteidae. 



Both the upper and lower jaws with teeth. Eyes without 

 lids. Maxillary bones absent. With permanent gills. 



Ex. Proteus, Necturus (the Mud-puppy or " Water- 

 lizard"). 



Family (3) Sirenidae. 



Both jaws are toothless. The hind-limbs, the maxillary 

 bones and the eyelids are absent. With permanent external 

 gills. 



Ex. Siren. 



Sub-order 2. Salamandroidea. Urodela. which in the 

 adult stage lose all trace of gills and gill-slits. 



Family Salamandridae. 



Both the upper and lower jaws are furnished with teeth. 

 Fore- and hind -limbs well developed. Eyes with movable lids. 



Ex. Molge, Salamandra, Desmognathus, Plethodon, Am- 

 blystoma. 

 s. & M. 36 



