236 CLASS xv. 



cold regions, whilst the last are the most limited to warm countries ; 

 the mean between these two extremes is formed by the lizards and 

 serpents. 



The fossil reptiles are of greater interest for the knowledge of 

 the secondary mountain strata than any other vertebrate animals; 

 most of the extinct lacertine animals occur in the Jura-lime, or in 

 the Liassic and oolitic formations ; in the tertiary formations some 

 remains of serpents and batrachians have been observed. 



