CERATOPS BEDS OF WYOMING AND MONTANA 293 



The Fort Union formation, properly restricted, is of early Eocene 

 age, the determination resting chiefly on its stratigraphic position 

 and its primitive mammalian fauna which is related to the earliest 

 I^ocene fauna of Europe. The very modern character of the flora 

 tends to confirm this correlation. 



The "Ceratops beds" are of Cretaceous age as decided by strati- 

 graphic relations, by the pronounced Mesozoic character of the verte- 

 brate fauna with absence of all Tertiary types, and by the close rela- 

 tions of its invertebrate fauna with the Cretaceous. The relations of 

 the flora with Eocene floras is believed to be less important than this 

 faunal and stratigraphic evidence. Taken in their whole areal extent 

 they probably include equivalents of the Laramie, Arapahoe, and 

 Denver formations of the Denver Basin. 



