B ATRAC HI A. 



308 



Class YII. — B ATRACHIA. 



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 appi-oach 

 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 ha\s 



Fig. 170. — Skull of Eri/ops tiw<jtwephnlu&, 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 res])ects, and in the 

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

 fer from this class in the presence of legs and absence of fins, aii<l in tlie 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 batrachian, there is always a period wiiicli follows 



