234 



GEOLOGY OF THE DENVER BASIN. 



has laid special emphasis on this different constitution of strata in discussing 

 the formations of the Yampa district in Colorado. 



The invertebrates of the Ceratops beds, found often in intimate 

 association with the dinosaurian remains, are thought by Mr. Hatcher to 

 be evidence of the Laramie age of the beds. He mentions five species 

 identified by Dr. C E. Beecher, and states that there are others. It is said 

 that some of them are "known from the typical Laramie," and some "are 

 characteristic of it." The weight of this evidence in the present discus- 

 sion clearly depends upon what is considered "typical Laramie." The 

 known distribution of the five species mentioned by Mr. Hatcher is given 

 in the subjoined table, prepared for the writer by Mr. T. W. Stanton, 

 accompanied by* sonic remarks on the localities, which are published with 

 Mr. Stanton's kind permission: 



Concerning these localities Mr. Stanton's comments are as follows: 



The locality on Crow Creek, northern Colorado, seems to be in the true Laramie, 

 and the Black Butte locality has usually been referred to the same formation. The 

 invertebrates from Black Butte come from beds below the dinosaurian remains, 

 according to Dr. White. The localities near Fort Union, Fort Clarke, Heart River, 

 and in the valley of the Yellowstone are in the Fort Union beds. The two species 

 from Lebo Creek are there associated with a number of other species that occur in 

 the original Fort Union area. The Weber, Utah, locality is in the Wasatch Eocene, 

 and that at Separation, Wyoming, is considered as probably Laramie by Dr. White. 



From the foregoing it is plain that the shells mentioned by Mr. Hatcher 

 do not serve as evidence for the Laramie age of the Converse County 

 beds as strongly as they show their intimate relation to the Fort Union 

 formation, now commonly regarded as Eocene. This fauna can not be 



