20 THE COMMON FROG. [chap. 



5. Pharyngobranchii (the amphioxus. or lancelet). 



Reptiles are arranged in nine different orders, 

 five of which are now entirely extinct. They are 

 i:^^ hVing forms : — 



1. CrocodiHa (crocodiles). 



2. Sauria (lizards, the Amphisbenae, the little 

 Flying-dragon, &c.) 



3. Ophidia (serpents). 



4. Chelonia (tortoises and turtles). 

 Of extinct kinds there are : — 



5. Ichthyosauria ; 6, Plesiosauria ; 7, Dicynodontia; 

 8, Pterosauria ; and 9, Dinosauria. 



The remaining class, Batrachia, will require more 

 lengthy consideration, both as a whole and as regards 

 the four orders which compose it, and which are 

 called respectively, I, Anoura ; 2, Urodela ; 3, Ophio- 

 morpha ; and 4, Labyrinthodonta. 



It will require such consideration, because it is 

 the class to which the Frog itself belongs. 



The Frog belongs to the Batrachian order Aiioura, 

 to the family Ranidce, and to the genus Rana. 



The order Anoura, to which all frogs and toads 

 belong, is a remarkably homogeneous one, consisting 

 as it does of a multitude of species, all differing from 

 each other by comparatively trifling characters. 



Altogether there are about 600 species of frogs and 

 toads, arranged in about 130 different genera. 



