210 



REPTILIA. 



and the teeth are pretty nearly equal in size and similar in 

 form in the two jaws. 



Fitr. oo9.— Skull of the Crocodile. 



The first appearance of Proccelian Crocodiles, so far as 

 known, is in the upper portion of the Cretaceous series of 

 North America, where they are represented by the genera 

 Bottosaurus, Holops, and Thoracosmi7ms, all of which are pe- 





Fig. 560.— Ujiper jaw of Alligator. Eocene Tertiary, Lsle of Wiyht. 



culiar to this formation. In Europe, however, the earliest 

 remains of Proccelian Crocodiles are from the Lower Tertiary 

 rocks (Eocene). It is a curious fact that in the Eocene rocks 

 of the south-west of England, there occur fossil remains of 

 all the three living types of the Crocodilia — namely, the 

 Gavials, true Crocodiles, and Alligators ; though at the pres- 



