THE COMANCHE AN PERIOD. 127 



Later Cretaceous period. Stated in other terms, the widespread sub- 

 mergence of areas which were land during the Early Cretaceous period, 

 marked the commencement of a new period, because it established 

 new geographic relations of great importance. It should be stated, 

 however, that the separation of the two systems in Europe, where 

 the Upper Cretaceous is often conformable on the Lower, is some- 



Fig. 383. — Sketch-map of Europe during the Xeocomian stage of the Early Cretaceous 

 period. The shaded areas are areas of deposition. (After De Lapparent.) 



what less pronounced than in North America. The Upper Cretaceous 

 is, however, much more widespread than the Lower. 



The Cretaceous systems of England, France, and other parts of 

 western Europe are best known, and the classification now some- 

 what generally accepted, though often with slight modifications, is 

 based on the formations of that part of the continent, and is shown 

 in the table on p. 109. 



In other continents, the Lower and Upper Cretaceous have not 

 always been clearly differentiated, yet enough is known to show that 



