CHAPTER XIII 



CORRELATION OF THE CENOZOIC THROUGH ITS 

 MAMMALIAN LIFE 



HENRY FAIRFIELD OSBORN 

 American Museum of Natural History, New York City 



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 

 data may be obtained as to secure common understanding and usage 

 of chronologic terms in the two countries. 



Previous to 1898 scattered attempts at the correlation of European 

 horizons inter se were made by Dawkins, Schlosser, Osborn, Deperet, 

 and others, but it was not until June, 1905, that there began in the 

 Comptes rendus a remarkable series of papers by Deperet entitled 

 " L'evolution des mammiferes tertiaires," covering with fulness the 

 whole subject of the succession of mammalian life in Europe, the 

 correlation of all the known horizons, with theories as to the migra- 

 tions between the continents of Eurasia, North America, and Africa. 

 I am not in accord with Deperet on many of these theories but I 



