THE CLASS EEPTILIA. 7 



The only existing forms of the class Eeptilia — there 

 are six extinct orders — are the following : — 



Order 1. Chelonia (tortoises and turtles), 



n 2. Lacertilia (lizards). 



.. 3. Ophidia (serpents). 



.1 4. Crocodilia (alligators and crocodiles). 



The curious New Zealand lizard is by some authori- 

 ties given an order to itself, but we need not concern 

 ourselves with that point. As we have already said, 

 our British reptiles are confined to the orders of ser- 

 pents and lizards, and there are three representatives 

 of each of these orders. 



These are as follows : — 



Order Lacertilia or Lizards: 



1. Lacerta vivipara, common lizard. 



2. Lacerta agilis, sand-lizard. 



3. An guis fr agilis, slow-worm. 



( >rder Ophidia or Serpents : 



1. Vipera hern*, the adder. 



2. Tropidonotus natrix, ring snake. 



3. Goronrlla austriaca, smooth snake. 



The lizards do not come into the scope of this 

 work, except in so far as their presence or absence 

 affects the snakes, a point to be dealt with later on. 

 They have been studied with great accuracy and 

 detail by various observers, and have a literature of 

 their own. 



