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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 whe 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. N. Y. Acad. Sci., xiii, pp. 9, 10); and in his latest matter 
on the subject he correlates the Torrejon with the Thanetian, or Cernay- 
sian (Bull. 361, U. S. Geol. Surv., p. 84). 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 equivalent of the Torrejon. Hence, wherever the latter is 
put the Fort Union or some part cf 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 Kocene they have lowered the base of the 
latter fofmation 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 EPpocH to THOSE OF PUERCO 
AND 'TORREJON. 
Inasmuch as those geologists and paleobotanists who fayor 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 question 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 
