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 

 of living forms : — 



1. Crocodilia (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 Frocr itself belong-.s. 



The Frog belongs to the Batrachian order Anoura, 

 to the family Ranidce, and to the genus Rana. 



The order Anoura, to which all frog-s 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. 



