THE CRETACEOUS PERIOD 273 



The Principal Surviving Mesozoic Reptile Groups 



Though overwhelmed by the Reptiles above described and of 

 less peculiar interest because they represent groups still living, 

 certain other Mesozoic Reptiles deserve brief mention. 



Turtles date back at least to the middle Triassic, and even 

 those very early forms clearly showed the familiar structure which 

 easily separates them from other Reptiles. 



Lizards are known even from the Triassic, and, though they 

 ranged through the Mesozoic, they were always small and com- 

 paratively rare. 



Crocodiles made their first appearance in the Jurassic, and some 

 were marine forms. In appearance they resembled the modern 

 Gavial of India, particularly as regards the long, slender snout. 

 Crocodiles were numerous from the Jurassic to the end of the 

 Mesozoic. 



Snakes are not known to have appeared till late in the Cre- 

 taceous, and those early forms were small and comparatively rare. 



