462 GEOLOGICAL SURVEY OF THE TERRITORIES. 



the fact that we already know that there is in Nebraska in clearly Qre- 

 taceous rocks, a tlora that was referred by the highest European author- 

 ity to the Miocene. 1 do not know, however, how far Professor Les- 

 quereux's opinion that the Bitter Creek plants are Tertiary may rest 

 upon specilic identidcatious among them of forms known to occur in 

 well determined Tertiary rocks elsewhere. 



TERTIARY AGE. 



Bniclcish-waler heels of Bear Elver*— In redemption of the promise 

 made, I now return to the consideration of the age of the brackish- water 

 beds of Bear Kiver, (division 28 of sec. — , on p. — .) These have al- 

 ways been regarded by me provisionally as Lower Eocene, not only 

 because their included fossil remains were closely related to forms 

 occurring in the Eocene lignite beds and deposits of the Paris Basin 

 and the month of the Rhone, but also because none of them belonged 

 to characteristic Cretaceous types. If, however, the beds of Bitter 

 Creek and the Judith Eiver should finally prove to be Cretaceous, 

 the brackish- water beds in question must probably be relegated to the 

 same epoch, though they are not known to hold any species in common 

 with the Bitter Creek beds, and but one with those of Judith lliver. 

 Their approximate conform ability with Cretaceous beds, indicating dis- 

 turbance and upheaval at the same time, favors this conclusion. I may 

 add that I have not been wholly without the suspicion that they might 

 prove to be Cretaceous, and in a report to Mr. Clarence King, published 

 in his report on the geological survey of the fortieth parallel, (vol. 3, p. 

 46G,) I summed up my conclusions in the following terms: 



While I anj therefore willing to admit that facts may yet be discovered that will warrant 

 the conclusion that some of these estuary beds, so widely distributed here, should be in- 

 eluded rather in the Cretaceous than in the Tertiary, it seems to me that such evidence 

 must either come from included vertebrate remains, or from further discoveries respect- 

 ino- the stratigraphical position of these beds with relation to other established hori- 

 zons, since alAhe molluscan remains yet known from them (my own opinions are en- 

 tirely based on the latter) seem to point to a later origin. 



This paragraph has been misunderstood by Professor Cope,t who has 

 brought it into context with the statement respecting the age of the Bitter 

 Creek coal strata, and asserted that the nearest approximation to the 

 point of identification of the Bitter Creek strata with the Cretaceous 

 were thus made by myself, and conveyed the impression that no positive 

 reference bad been made of any of the Bear River beds to this period. 

 This, however, as has been shown elsewhere, had been done in the most 

 unequivocal manner with regard to the deposits of marine coal at Bear 

 River City, Wyoming, as well as at Coalville, Utah. 

 ' I had intended to make more extended remarks on the several Ter- 

 tiary deposits referred to, and to have given lists of fossils from them, 

 but sudden illness, and the necessity for sending copy without further 

 delay to the Public Printer, have compelled the relinquishment for 

 the present of such design. 



* Until some decidedly Cretaceous fossils have been somewhere found in or above 

 these beds, they may be left in the lower Eocene. Our discovery of a group of fresh- 

 water shells as modern in appearance as these (though all different species) at Coal- 

 ville, far down in tlie Cretaceous, shows how cautious we should be iu deciding such 

 questions. 



t Proceedings American Philosophical Society. Extras dated in MSS. February 7, 1873. 



