230 KNOWLTON 



of the dinosaurs passing up into the Tertiary, and it would seem that 

 the time had come to demand something more tangible than mere 

 assumption for the Cretaceous age of the dinosaurs. 



Hatcher/' in speaking of the Ceratops fauna, frankly stated that 



owing to the fact that very few vertebrates had previously been 

 described from the typical Laramie, as first defined by Mr. Clarence 

 King, and the consequent lack of vertebrate forms known to have 

 come from the Laramie for comparison with those found in the Cera- 

 tops beds, it must be admitted that the vertebrate fauna of the latter 

 is, in itself, at present not sufficient proof to establish the Laramie 

 age of the Ceratops beds. 



In the Denver Basin, where, as already set forth, the relation of the 

 Laramie to underlying and overlying formations has been thoroughly 

 and satisfactorily elucidated, the dinosaurs have not been found in 

 the Laramie, though they are found in both Arapahoe and Denver 

 formations. During pre-Arapahoe time, as Cross has shown, there 

 was inaugurated the profound orogenic movement which originated 

 the Rocky Mountains and a period of erosion which cut through 

 many thousands of feet of strata before the beginning of deposition 

 in the Arapahoe Lake. The vertebrate paleontologists do not 

 appear to appreciate the significance of this great erosional interval 

 and its attendant phenomena. Mr. Cross" has so admirably stated 

 these conditions and the inference to be drawn from them, that I 

 cannot refrain from quoting his words: 



The dinosaurs of the Ceratops beds are highly modified and special- 

 ized forms unknown as yet in other parts of the world except, per- 

 haps, in the Gosau^^ formation of Austria, and the conclusion that 

 they necessarily indicate a Mesozoic age implies some reason why 

 they may not have survived into the early Tertiary. 



In the light of the facts which have been presented concerning the 



" Am. Jour. Sci. (3), vol. 45, 1893, p. 140. 



** Mon. U. S. Geol. Surv., 27, 1896, p. 251. 



*' The Gosau beds near Vienna, Austria, are usually referred to the upper 

 Turonian or lower Senonian. They are overlain by several hundred feet of 

 fossiliferous marine Cretaceous, and the dinosaur fauna, together with the 

 associated fossil plants, indicate an age that is approximately that of the 

 Judith River. 



Prof. R. S. Lull (in Hit., January 19, 1909) coincides with this conclusion 

 as to the stratigraphic position of the beds. 



