236 KNOWLTON 



Fortunately the work of Hatcher,^^ published as late as 1905, has 

 left us with a very complete annotated list of the Judith River forms, 

 which makes a valuable basis for comparison of the two faunas. 

 It needs, however, but a cursory examination to show that at least 

 half of the species listed as belonging to the Judith River do not be- 

 long to this fauna at all, but come from the Fort Union, Arapahoe, 

 etc., or are so fragmentary as to be unidentifiable. When there is 

 added to this the possibility of the truth of Professor Osborn's^^ con- 

 jecture that there has probably been a mixture of horizons in the 

 so-called Judith River fauna, any comparison of the turtles of the 

 Judith River formation with those of the "Ceratops beds" as tend- 

 ing to support the Cretaceous age of the latter, does not make a very 

 impressive case. 



d Fishes. 



The few and fragmentary fish remains from the " Hell Creek beds" 

 were studied by Dr. C. R. Eastman and Dr. L. Husakof. Con- 

 cerning them Eastman says: "As a whole the collection does not 

 have a decided Cretaceous aspect, " and adds that "it would be 

 useless to argue from this that the beds in question are of Eocene 

 age, for there are numerous fishes of preponderating Eocene type 

 in the Fort Benton Cretaceous of Wyoming." From this it appears 

 that the fish remains are not likely to be much of a factor in fixing 

 the age of these beds, though if anything they favor the Eocene age. 



Line Between Cretaceous and Tertiary. 



All things considered it seems that the logical point at which to 

 draw the line between the Cretaceous and Tertiary is at the top of 

 the true Laramie. If a locality could be found at which sedimenta- 

 tion was continuous, it would probably be necessary to draw an 

 arbitrary line, but we do not yet know any section of such complete- 

 ness in this country. In favor of placing it at the point indicated, 

 we have the evidence of diastrophism as signalized by the upbuilding 



*' Bull. U. S. Geol. Surv., 257, 1905, pp. 72-80. 



" Geol. Surv. Canada: Contr. Can. Pal., vol. 3, pt. 2, 1902, pp. 8, 9. 



