the Cretaceous-Tertiary Problem. 225 



maxima that must be the standards. Correspondence 

 in the sequence of diastrophic movements by no means 

 proves their synchronism. A correct interpretation of 

 the f aunal changes is the only means whereby this can be 

 proven. The initiation of diastrophism is demonstrably 

 far from synchronous in different regions ; it cannot well 

 serve as a basis for world-wide time divisions. Lee has 

 strongly insisted that the Tertiary as a whole (beginning 

 with the Lance and Paleocene) is a period of continuous 

 and increasing diastrophism.^^ But this, however true 

 of certain parts of the Rocky Mountain region, is totally 

 at variance with the stratigraphic record in other regions, 

 or with the inferences from the history of the land verte- 

 brates, which accord far better with the views outlined 

 by Schuchert in 1909. 



It appears from the above outline of present evidence 

 that the base of the true Eocene is the proper dividing 

 line on both theoretical and practical grounds between 

 Cretaceous and Tertiary; that the Paleocene and the 

 latest dinosaur faunas are best regarded as the upper- 

 most Cretaceous. They might be referred to a distinct 

 post-Cretaceous system as advocated by Cope, if the 

 evidence of a widespread stratigraphic break between 

 them and the Judith be regarded as sufficient. But the 

 vertebrate fauna lend no support to the view that there 

 was a distinct post-Cretaceous period. In any event, 

 they are not true Tertiary, and to call them Eocene is to 

 confuse two widely different faunae, one of Mesozoic and 

 the other of Cenozoic type. 



Value of the Vertebrate Evidence. 



The foregoing discussion has been confined to the ver- 

 tebrates and their interpretation, not from any desire to 

 minimize the importance of other data, palasontologic, 

 stratigraphic or tectonic, but because it is the group in 

 which I can lay claim to some special competence. Most 

 of the evidence is in the American Museum, in my charge, 

 and I have been working and studying on various parts 

 of it for twenty-five years. It is a matter of regret that 

 so much still remains inadequately published or illus- 

 trated, and that in consequence the statements made here 



22 Lee, 1915, IJ. S. Geol. Sur., Prof. Pap. 95, p. 57; 1917, idem No. 101, 

 p. 11. 



