16 BULLETIN 169, UNITED STATES NATIONAL MUSEUM 



now well established. In 1902 he appUed the name "Fish Creek Beds" 

 to the next higher division but later accepted their equivalence to the 

 Judith River as established by Stanton and Hatcher (1905). Douglass 

 (1909) continued to use the name "Fish Creek" for beds transi- 

 tional between Judith River and Bearpaw, but this name is not now 

 in general use. 



Lennep is a local name applied by Stone and Calvert to beds perhaps 

 equivalent to the Fox Hills but not definitely correlated. In physical 

 character they resemble the Lebo, and seem to grade into the Livingston 

 laterally. 



Cretaceous — Tektiaey Transition 



It is not proposed to discuss here the general evidence for drawing 

 the boundary between the Cretaceous and the Tertiary, a problem to 

 which this field contributes only one small part, and not the most 

 important part. For present purposes it is assumed that beds up to 

 and including the true dinosaur-bearing Lance and Hell Creek and 

 their equivalents belong in the Cretaceous and that overlying beds 

 without dinosaurs (except by redeposition) and with mammals of 

 Tertiary type (including carnivores, condylarths, etc.), from the 

 Puerco and its equivalents upward, are to be placed in the Tertiary. 

 It is also assumed that the Paleocene is accepted as a separate epoch 

 of the Tertiary, of equal rank with the Eocene, Oligocene, Miocene, and 

 Pliocene, and that its lower limit is taken as the base of the Puerco 

 or equivalent, or the top of the (restricted) Lance or Hell Creek or 

 their equivalents, and its upper limit at the top of the Clark Fork, or 

 equivalent, or base of the Sand Coulee and Gray Bull, or equivalents. 



On these assumptions, which I believe to be based on the most 

 reasonable and useful interpretation of all the evidence, it is here pro- 

 posed only to discuss briefly the beds in this field that must include 

 the transition from Cretaceous to Tertiary as thus defined and to 

 suggest where the boundary may occur in this local series. 



The following is a somewhat generalized section from the Hell Creek 

 into the Fort Union No. 1 in sec. 26, T. 6 N., R. 16 E., passing through 

 Loc. 65 and near Loc. 78, about 2 miles northeast of the northern 

 end of Bear Butte: 



Horizon of Loc. 78 



Feet 



Mostly greenish shales and sandy shales 30 



Somber cross-bedded sandstone, the upper part bard and ridge- 

 Fort forming 40 



Union < Somber greenish shale and sandy shale 85 



No. 1 Same, with bone fragments including unidentifiable mammals 



of Tertiary aspect, Loc. 65 7 



Same, without fossils 35 



197 



