CHAPTER II 



THE ORDER LACERTILIA 



DEFINITION OF LIZARD CLASSIFICATION GENERAL 



FACTS. 



Although one can arrive at a definition of an order 

 of animals only after minute consideration of their 

 structure and relationships, it will be simpler for 

 our present purpose to define what we mean by a 

 lizard at once, and then see how that definition is 

 arrived at. 



Definition. — Lizards are Saurians which have the 

 right and left halves of the lower jaws connected by 

 a bony suture. 



Such a definition indicates at once that structural 

 characters alone are to be relied upon for classifica- 

 tion. It also indicates that we cannot understand the 

 definition of any one order of animals unless we also 

 understand the definitions of other groups. In this 

 particular case it becomes necessary to know what 

 Saurians are before we understand what is meant by 

 a lizard. It will be sufficient, perhaps, for our 



