284 STANTON 



malian fauna and that of the "Laramie" is greater than that between 

 the Puerco and Wasatch mammals. 



The Puerco formation of New Mexico lies between the Laramie and 

 the Wasatch and contains two faunal zones. To the upper of these 

 the vertebrate paleontologists have applied the nameTorrejon, restrict- 

 ing Puerco to the lower one. It has been shown that in Montana the 

 Fort Union formation includes mammal-bearing beds with a fauna 

 more closely related to the Torrejon fauna than to the restricted Puerco 

 but this probably does not mean that only the upper zone is strati- 

 graphically represented. It is fair therefore to say that the Puerco 

 as a whole is in Montana stratigraphically above the " Ceratops beds." 

 The Puerco is now generally treated as basal Eocene, though Cope 

 called it Mesozoic and placed it with the Laramie in a separate sys- 

 tem beneath the Tertiary, and if it is basal Eocene then the Ceratops 

 beds should be Cretaceous on that showing alone. 



Osborn^* says of the restricted Puerco that its mammalian fauna 

 is " wholly of Mesozoic origin, and mostly destined to disappear; not a 

 single representative or ancestor of any existing orders of Tertiary 

 mammals is certainly known" and that it has no representative in 

 Europe. Concerning the Torrejon mammals he says that out of 40 

 species only one is of "modernized Tertiary stock," all the others being 

 Mesozoic, i.e., derived from and related to the Mesozoic. The 

 Torrejon is compared with the Thanetien or Cernaysien stage of 

 France. Apparently it would do less violence to the vertebrate e\i- 

 dence to put the Puerco and Torrejon horizons in the Cretaceous than 

 to put the "Ceratops beds" in the Tertiary. 



In France the Montien stage now referred to the uppermost Cre- 

 taceous contains dinosaurs closely related to those of the Tricera- 

 tops fauna, according to De Lapparent.^^ 



The vertebrate evidence for Cretaceous age does not rest on a single 

 dinosaur or a few members of that group associated with a Tertiary 

 fauna. If this were the case it would be fair to argue that they were 

 straggling descendants of an earlier fauna that had lived beyond their 

 normal time. The whole fauna is Cretaceous in its affinities and the 

 fair question is not could the dinosaurs have lived on into the Tertiary, 



*" Osbom, H. F. : Cenozoic mammal horizons of Western North America' 

 Bull. U. S. Geol. Survey, No. 361, 1909, pp. 34, 35. 

 '•' Traits de Geologic, 5™^ ed., 1906, p. 1472. 



