ORDERS OF AMPHIBIANS 65 



OEDEES OF AMPHIBIANS , 



Note. — ^If the specimen is not described at the single letter, say A, 

 go on to where the letter is doubled, as AA. 

 A. Skull roofed with bone — at least behind the eye. Teeth often 



wrinkled. Fossil. Stegocephala. 



AA. Skull not so roofed. 



B. Legs absent. C^cilians. 



BB. Legs present two or four. 



C. Tail present. Salamander-forms. 



CC. Tail absent. Frog-forms, 



D. Tongue present. 



E. Gristles of breast-bones overlapping. 



Suborder Toads. 

 EB. Gristle of breast-bone not overlapping. 



Suborder Frogs. 

 DD. Tongue absent. 



Suborder Tor^gueless Frogs. 



The salamander-forms are divided into families by various 

 modes of olassifloations, based on anatomical difEerences ; but the 

 following simple artificial key will, by outside features purely,- 

 lead to the families (as now divided) : 



TAILED FORMS 

 A. Outside gills gone in the adult. 



B. Eyelids present, no gill-opening (the real salamander-forms). 

 C. Tail round — no fin. Salamanders. 



CC. Tail flat — with a fin above. Newts. 



BB. Eyelids absent. 



D. Toes two or three behind and three in front. 



Congo Snake. 

 DD. Toes five behind, four in front. 



Giant Salamander. 

 AA. Outside gills present in adult. 



E. Limbs four. (Proteus), Mud-puppies. 



EE. Limbs two. ' Sirens. 



The frog-forms have their suborders scientifically divided 

 into many families, genera, and species. The discussion is too 

 great for our space and too technical for our plan. 



