214 HENRY F. OS BORN 



Second or mid-Pleistocene fauna, Eolithic and early Paleolithic 

 Stages; 



Third or Upper Pleistocene fauna, late Paleolithic Stage ; 



Fourth, post-Glacial fauna, Neolithic Stage. 



From close study of the Pleistocene life of North America there is 

 promise of correlation with Europe through identification of x\merican 

 with European glacial- and interglacial periods, through the discovery 

 and identification of interglacial faunas, as in the Aftonian and 

 Toronto deposits, through the careful recording of the time of extinc- 

 tion of native types and of the time of arrival of new types to demarkate 

 our Pleistocene also into great successive life-zones. 



The chief progress made thus far (1909) is that we begin to recog- 

 nize the following divisions of American life: 



Early and mid-Pleistocene life of the plains, Equus Zone; 



Mid-Pleistocene life of the forested regions, Megalonyx Zone; 



Life of the maximum cold period, Ovihos Zone; 



Life of post-Glacial times, Zones of Cervus and Homo. 



Especially interesting is the coincidence of the maximum cold 

 period, or Ovihos, Musk Sheep Zone of America, with the maxi- 

 mum cold period, or Elephas primigenius, Rangijer tarandus Zone of 

 Europe. 



It is obvious that we should never expect to discover as clear 

 demarkation of the life-zones in America as in Europe because of the 

 vast refuge areas of the mammals in the south. In Europe the 

 glacial advances are sharply punctuated by the appearance and 

 disappearance of species. In America apparently such appearances 

 and disappearances are gradual. 



PRINCIPAL REFERENCES 



Deperet, Charles, "L'evolution des mammiferes tertiaires," Compt. Rend. 



Acad. Sci., Paris, June 5, July 3, November 6, 1905, March 12, 1906. 

 OsBORN, H. F., "Correlation between Tertiary Mammal Horizons of Europe and 



America; an Introduction to the More Exact Investigation of Tertiary 



Zoogeography; Preliminary Study, with Third Trial Sheet," New York 



Acad. Sci. Ann., Vol. XIII (1900), pp. 1-64. 

 , "Cenozoic Mammal Horizons of Western North America," U. S. Geol. 



Surv. Bidl. j6i (1909), pp. 1-138. 



