AMPHIBIA 427 



boniferous. At the present time the Amphibia are represented by 

 the dwarfed and specialized frogs and toads, newts and salaman- 

 ders, which give but an imperfect notion of the structure of the ex- 

 tinct members of the class. The Carboniferous Amphibia all belong 

 to the extinct order Stegocephala, in which the skull is well covered 

 with a roof of sculptured bones,^ and which are of moderate or 

 small size, not exceeding seven or eight feet in length and mostly 

 much smaller. The backbone is not ossified, the limbs are weak, 

 the tail short and broad, and in many forms the belly is pro- 

 tected by an armour of bony scutes. An extraordinary number of 

 genera of Carboniferous Stegocephala are known, most of them 

 like the Salamanders in shape, but some are elongate, slender, 

 and of snake-like form. Examples are Archegosaurus, Branchi- 

 osaurus, Dendrerpeton % Ptyonius, and many others. 



