THE 



JOURNAL OF GEOLOGY 



APRIL-MAY, 1910 



CORRELATION OF THE CENOZOIC THROUGH ITS 

 MAMMALIAN LIFE 



HENRY FAIRFIELD OSBORN 

 American Museum of Natural History, New York City 



XIII^ 



The sea borders of the United States may be correlated with each 

 other and with those of Eurasia in Cenozoic times through their 

 invertebrate life, but for the vast interior of the American continent 

 we must depend chiefly upon the mammals and in a less degree 

 upon the reptiles, fishes, insects, and plants. I foresee great aid 

 through these latter sources, but it is clear that the mammals will 

 always afford the chief means of correlation, since in all parts of 

 Europe mammal-bearing formations alternate with marine shell- 

 bearing formations. 



The standard divisions of Cenozoic geologic time will always be 

 those established in Europe. The problem set before the paleontolo- 

 gists of our country is therefore to compare and establish our time 

 divisions as closely as possible with the European standards. For 

 this reason since 1899 I have been pursuing an exact investigation 

 of the sequence of mammalian life in America and in the European 

 Tertiary formations, and have enlisted the co-operation of many 

 European and American paleontologists in the hope that such precise 



I This article, which should have appeared as No. XIII in the series of correla- 

 tion papers published last year, did not reach the Journal of Geology in time to be 

 published in its proper place, in No. 7, 1909. 

 Vol. XVIII, No. 3 201 



