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series that lias been called Laramie and in the Fort Union. Again, they 

 are found in the Green River beds, in the White River beds, and in the 

 deposits at Florissant. Colorado. Otherwise, the record is mostly missing. 

 On the other hand, the history of the vertebrates is quite full. Between 

 the Fox Hills and the present time there are known probably nearly twenty 

 distinct faunas and it has been found possible to correlate these in most 

 cases closely with European faunas. With such a series at command, the 

 extremes of which differ enormously, while the mean terms sometimes 

 grade into their successors, at other times differ greatly from the next 

 comers, the paleontologist need not go far astray in determining the proper 

 level of each fossil-bearing deposit. It may be remarked that when the 

 paleobotanist refers the Green River beds to the Oligocene, while the ver- 

 tebrate paleontologists put them at the bottom of the middle Eocene, a 

 serious dislocation of views is indicated. 



7. The Beginning of the Eocene in Europe and America. 



When one comes to correlate formations in America with those of 

 distant countries great difficulties are likely to be experienced. Interrup- 

 tions in stratification are 'not likely to occur at the same time in America 

 and Europe and Asia. On account of differences in the character of the 

 deposited materials, the climate, the interposition of barriers, and other 

 features of environment, the contained organisms must differ to a greater 

 or less extent. In the case of the beds about which exists our dispute, 

 they are neither of marine origin nor in contact with strata of purely 

 marine origin. Hence they cannot be compared directly with either the 

 typical uppermost Cretaceous deposits of Europe, the Danian, nor with 

 the Thanetian. the lowermost European Eocene. The Lance Creek beds, 

 the Hell Creek beds, and others related to them have been produced 

 mostly through the action of fresh waters and they contain remains of land 

 plants, freshwater mollusks and fishes, reptiles inhabiting the water and 

 the land, and a few terrestrial mammals. In such a situation we must 

 have recourse to indirect means of correlation. 



In the vicinity of Rheims. France, in deposits belonging to the Thane- 

 tian, there has been found a considerable number of genera and species 

 of extinct mammals, together with some birds, reptiles, and fishes. The 

 mammals have been studied and described by Lemoine. On the strength 

 of this fauna these Cernaysian beds were correlated with the Puerco at a 



[19—23003] 



