MATTHEW, CLIMATE AND EVOLUTION 



245 



In the later Oligoeene of Europe and the Miocene of the United States 

 appear more definitely deer-like types {Dremotheriuni, Blastomeryx) , 

 and in the succeeding formations we find progressively higher types of 

 deer in Europe and North America, but always appearing earlier in the 

 Old World. The deer — excepting the isolated primitive survival repre- 

 sented by the "water-chevrotain," closely related to Dorcatherium, a 

 Miocene genus in Europe — have not reached the Ethiopian region, but 



77tid-Tcrtiaru ■ Cerv/. 

 in. laTer T'erfi'a 



Cervidae. in 

 later Tertiarij 



/Yb Cervidae 

 until Plet's toe 6716 



Huae moscA us 

 (cf.J)orcal/>'m) 



'Ran^ifer,Alces, Ceri/us cancLdensiS and a 



ItiiS 



>S^^ Ot/ier Cervidde ^prirnitd^t ty/jcs jnostty i>z tropics 



Fig. 23. — Distribution of Cerridop and pro-Cervid Tragulidw 



The liighest and latest appearing types are stlU confined to the circum-Arctic regions ; 

 the genera of the more peripheral regions are more primitive. The earliest and most 

 direct ancestral series is found in Europe and Asia ; the parallel series in North America 

 is less direct and more retarded. A primitive survival is found in West Africa, pro- 

 tected by the desert from competition of higher types. 



were easily able to reach ISTorth America in the Pleistocene. I take it, 

 therefore, that their center of dispersal was well to the east and north in 

 Asia (cf. horses). Their migration into the Ethiopian region was checked 

 after the Miocene by the progressive aridity of the desert region between. 



