234 The Upper Cretaceous Floras of the World 



The Colorado Group 1 



The Dakota sandstone is overlain by the Benton shale and this in turn 



throughout a part of its area by the Niobrara limestone, both marine 



deposits carrying abundant faunas but no land plants. Together they 



consitute the Colorado group of the classic section of Meek and Hayden, 



and they are more or less loosely correlated with the Turonian and 



Emscherian stages of the European section. On the boundary between 



the Colorado and Montana groups, or perhaps representing a part of the 



westward littoral phase of the Niobrara chalk of the more easterly part of 



the Interior basin is the Eagle sandstone from which the following plants 



have been described : 2 



Ficus missouriensis Knowlton 



Juglans ? missouriensis Knowlton 



Laurus ? sp. 



Liriodendron datum Newberry 



Platanus wardii Knowlton 



Protophyllocladus polymorphus (Lesquereux) Berry 



Quercus ? montanensis Knowlton 



The Montana Group 1 



Overlying the Eagle formation in the western part of the Interior basin 

 the following series of formations have been differentiated, i. e., Claggett, 

 Belly River or Judith River, and Bearpaw. These arc represented to the 

 eastward by the Pierre formation. Overlying this is the Fox Hills sand- 

 stone which is the topmost member of the Montana group. Both this and 

 all other Upper Cretaceous horizons in the province in accordance with 

 the official practice of the U. S. Geological Survey have received local 

 formation names too numerous to be considered in the present brief 

 review. The reader who desires to pursue this subject in detail is referred 

 to the excellent summary contained in the explanatory text for the geo- 

 logical map of North America, 3 where the literature is fully cited. The 



1 There is no geologic or paleontologic basis for the term Colorado group or 

 Montana group. 



2 List furnished by F. H. Knowlton of the U. S. National Museum. 



3 Index to the stratigraphy of North America. Prof. Paper U. S. Geol. Sur- 

 vey No. 71, 1912. 



