BATRACHIA. 



303 



Class VII. — B ATKACHIA. 



This class of Vertebrata is intermediate in characters, and therefore in position, 

 between the fish-like forms and the reptiles. Among the former the Dipnoi approach 

 it most nearly, while the extinct reptiles of the oldest order, the Theromorpha, are the 

 nearest allies on the reptilian side. It belongs to the series of vertebrates which have 



^^V" 4- 



Eia. 170. — Skull of Enjqps inegacephalus, one fifth natural size. 



a distinct coracoid bone in the shoulder girdle ; and a distinct quadrate bone in the 

 skull. The greater 'part of the basicranial axis is cartilaginous, but it is protected 

 below by a membrane bone, called the parasphenoid. In all these respects, and in the 

 absence of an allantois of the embryo, the Batrachia agree with the fishes. They dif- 

 fer from this class in the presence of legs and absence of fins, and in the absence of 

 various bones which belong to the branchial and opercular systems, and to the sus- 

 pensor of the lower jaw. 



In the course of the growth of a bati-achian, there is always a period which follows 



