340 r. H. KNOWLTOX CRETACEOUS-TERTIARY BOUNDARY 



may be a recurrent fauna surviving from the Fox Hills fauna, which is 

 itself partially recurrent from the Claggett (lower Montana). But this 

 explanation requires a connection with the sea, presumably after the in- 

 auguration of Eocene time. 



Conclusions 



The thesis of this paper, as stated at the beginning, is that the line 

 between Cretaceous and Tertiary in the Eocky Mountain region is to be 

 drawn at the base of the dinosaur-bearing and equivalent beds^that is, 

 at the base of the Lance, "Ceratops beds,^' "Hell Creek beds/' "Somber 

 beds,'' Arapahoe, Dawson, Eaton, and "Laramie" of many writers. Evi- 

 dence, believed to be competent, has been presented in support of this 

 view from the side of stratigraphy, diastrophism, and paleobotany, and 

 what is thought to be the weakness and insufficiency of the vertebrate and 

 invertebrate evidence has been pointed out. The vertebrate paleontolo- 

 gist would place the Cretaceous-Tertiaiy line at the highest horizon at 

 which dinosaurs are found, notwithstanding the fact that this is a vari- 

 able boundary unattended by structural or diastrophic action. The in- 

 vertebrate paleontologist would place this line at the highest point where 

 marine invertebrates of Cannonball types occur. The paleobotanist would 

 place the line at the lowest horizon at which Tertiar}^ plants have been 

 found which corresponds with the structure. The paleontologists are not 

 in accord. It is unlikely that they will ever be in complete agreement. 

 What, then, is to be the court of final appeal? There is but one answer: 

 Structure resulting from diastrophism. The evidence from these sources 

 supports the thesis. Why, then, shall we not be logical and rational, and 

 agree to place the line where nature plainly indicated it rather than at 

 some shifting, vague, and indefinite point simply to maintain a tradition? 



