188 NEW YORK ZOOLOGICAL SOCIETY. 



relates to mammals, adduced by the advocates of this theory, 

 lies hi the singular and simultaneous appearance in Europe and 

 in America of the same types of animals, the hypothesis being 

 that these animals came from a common boreal home. 



As will appear below in the detailed consideration of our va- 

 rious animals, the place of origin of each group, based on positive 

 and not on negative evidence, can be found in practically all 

 cases. There can be no serious doubt, for instance, that the bear 

 originated and developed in Eurasia. The same is true of the 

 cats comprising the type genus Felis, and of the great deer 

 genus Cervus. 



In fact the only American animals about the origin of which 

 there is much doubt, are the moose and the caribou. These two 

 undoubtedly originated and attained their development in some 

 far northern land. It is not necessary, however, to assume a 

 polar continent for these two genera, as the existing land areas 

 to the north of the American continent, or that portion of Siberia 

 lying within the Arctic Circle with the recently submerged and 

 adjacent coast, would supply boreal land areas quite sufficient 

 in extent for the development of these types. 



TYPE DIVERGENCE. 



In carefully considering the various types of North American 

 mammals a very important clew to their origin can be found in 

 the degree of differentiation which each one of these animals has 

 achieved. It would appear that this degree of radiation and of 

 departure in structure from their Old World kindred would in 

 some measure correspond to the amount of time which has elapsed 

 since the first appearance of these animals in North America. 

 The deductions in this article are based on these lines of reason- 

 ing, and the conclusions are in most instances confirmed by the 

 fossil record. 



When we find, as in the case of the genus Cervus, of which our 

 sole American representative is the wapiti, that the Old World 

 has about twenty species belonging to this genus and to closely 

 allied genera ; that is, one species as an inhabitant of the New 

 World, against about twenty in the Old World (and some of 

 these Old World species, like the Altai wapiti from Mongolia, 

 are very closely akin to the American wapiti) ; when we can go 

 from England eastward through Germany, Hungary, the Cau- 

 casus and the mountains of Central Asia, and find the red deer 

 growing larger and finer, and fading imperceptibly through one 



