290 



time when this term was applied to beds now separated and known as 

 Puerco and Torrejon. There is thus furnished a means of beginning a 

 correlation of our land and freshwater Tertiary deposits with those of 

 Europe; but we need ever to keep in mind the possibilities of error. 



I believe that any one who may carefully compare the Cernaysian 

 fauna with the faunas of our Puerco and Torrejon must conclude that the 

 Cernaysian corresponds more closely with that of our Torrejon than with 

 that of the older Puerco. I find that Osborn had reached this conclusion 

 in 1900 (Ann. X. Y. Acad. Sci,, xiii. pp. 0, 10) : and in his latest matter 

 on the subject he correlates the Torrejon with the Thanetiau, or Cernay- 

 sian (Bull. 361. U. S. Geol. Surv., p. 34). Indeed, it seems not improbable 

 that the Cernaysian is a little more recent even than our Torrejon. 



It has been demonstrated that at least a part of the Fort Union for- 

 mation is the erpiivalent of the Torrejon. Hence, wherever the latter is 

 put the Fort Union or some part of it must go. The base of the Tertiary 

 being drawn in Europe at the bottom of the Thanetian, there appears to 

 be no good reason why in our country it should not be drawn above the 

 Puerco. possibly above the Torrejon and the Fort Union. Certainly, when 

 geologists and vertebrate paleontologists have consented to include the 

 Puerco and the Torrejon in the Eocene they have lowered the base of the 

 latter formation to its extreme level. To include now in the Eocene the 

 "Ceratops" beds, the Hell Creek beds, the Arapahoe and the Denver, 

 would be to add to it some hundreds of feet of deposits which, in the 

 opinion of vertebrate paleontologists, contains a considerably older fauna 

 than that occurring in the Cernaysian beds, and which with equal confi- 

 dence the invertebrate paleontologists refer to the Cretaceous. 



8. Relationship of Fauna of Lance Creek Epoch to Those of Puerco 



and Torrejon. 



Inasmuch as those geologists and paleobotanists who favor the trans- 

 ference of a large part of the Laramie (as formerly understood) to' the 

 Tertiary insist that the fauna of the Lance Creek and the Hell Creek beds 

 is more closely related to that of the Puerco and that of the Torrejon than 

 to any Cretaceous fauna, this cpiestion must be considered. With regard 

 to the relationships of the mammals of the Lance Creek beds to those of 

 the Puerco and Torrejon extremely diverse views have been expressed. 

 Marsh (Amer. Jour. Sci.. xliii. 1892, pp. 250, 251) says that the mammals 

 of the Lance Creek deposits 



