260 



HISTORICAL PALEONTOLOGY. 



GENERALISED SECTION OF THE CRETACEOUS SERIES 

 OF BRITAIN. 



Eocene. 



White Chalk with Flints. 



\~- White Chalk without Flints. 



- -Chalk Marl. 



Upper Greensand. 



Gault. 



Lower Greensand or Neo- 

 comian. 



. _ ....Weald Clay. 



Wealden Series. 



- Hastings Sands. 



In North America, strata of Lower Cretaceous age are well 

 represented in Missouri, Wyoming, Utah, and in some other 

 areas ; but the greater portion of the American deposits of 

 this period are referable to the Upper Cretaceous. The rocks 

 of this series are mostly sands, clays, and limestones Chalk 

 itself being unknown except in Western Arkansas. Amongst 

 the sandy accumulations, one of the most important is the so- 



