THE EOCENE OF EUROPE AND NORTH AMERICA 



153 



peckers, cuckoos, rollers, etc., the Gallinae, 

 or gallinaceous birds, the Grallai, or shore- 

 freciucnting birds, and finally of the Stega- 

 nopodes, which include the corniorants/ 



Middle and Upper Eocene of the 

 Rocky Mountain Region 



The whole vertebrate fauna, reptilian as 

 well as mammalian, of this period is better 

 known than that of any other of the Eocene 

 phases. As shown in the correlation table 

 (Fig. 10, p. 49) the Middle and Upper Eocene 

 is represented by a grandly successive series 

 of formations, partly overlapping in time, 

 and apparently leaving no interval unfilled 

 with records of mammalian life. Reading 

 fi-om the base upward, these formations suc- 

 ceed and overlap each other as follows: 



Uinta, of northern Utah, including three 

 levels 



Washakie, of south central Wyoming, 

 including two levels 



Bridger, of southwestern Wyoming, in- 

 cluding two main levels 



Huerfano, of southeastern Colorado, 

 including two levels. 



Mammalia?! life. — Like the Middle and 

 Upper Eocene of Europe, the mammalian 

 life of the Rocky Mountain region of North 

 America is a unit. Of the twenty-six families 

 of mammals of every kind, seven cease to be 

 known at the end of the Midflle Eocene or 

 Upper Bridger phase. Only two new families 

 are suddenly introduced at the summit of 

 the Eocene or Upper Uinta phase. There 

 was thus in the Rocky Mountain region a 

 long period of uniform evolution and com- 

 petition among the members of the existing 

 fauna, a few families l)ecoming extinct and 

 the majority surviving with no sudden in- 

 troductions of dangerous coin])etitors. On 



' Owen, Palffiontology (1860), pp. 291-292. 



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