110 ORIGIN OF LIFE IN AMERICA 



northern hemisphere, and that they are comparatively modern 

 immigrants into South America, where they now attain their 

 maximum development. 



Mr. Lydekker gets over the difficulty of the simple-antlered 

 South American deer, or brockets as they are calleld, by the 

 admission that because they are unknown in North America, 

 they are not ancestral forms. He thinks they should be 

 regarded as degraded or arrested types of the group (p. 296). 



Professor Marsh * was inclined to look upon the North 

 American Leptomeryx as the probable progenitor of the 

 Cervidae. His suggestion led to further researches on the 

 part of Dr. Matthewf who supplied a connecting link in the 

 chain of ancestry of Odoicoileus in the Miocene Blastomeryx. 

 That Dr. Matthew's view, however, is not generally accepted 

 may be gathered from Professor Osborn's J recent remark in 

 reference to the Pleistocene Period in North America, that 

 among the newly entering northern forms are Odoeoileus, 

 Ursus and Erethizon. Professor Osborn's § opinion is that 

 the origin of the Cervidae will probably prove to be Asiatic. 

 I quite concur in the view that they are of Old World origin, 

 and yet I hold that the ancestors of the North American 

 Odoeoileus have invaded the northern continent from South 

 America. The remote ancestors of Odoeoileus must, there- 

 fore, have penetrated from the Old World to South America 

 without attaining North America. How they have done so is 

 the problem I shall endeavour to solve. 



Later on, when we come to deal with the zoogeographical 

 relationship of South America and Africa, I shall show that 

 we possess valuable evidence for the belief in a former land 

 connection across the southern Atlantic between these conti- 

 nents. This, however, will not help us in explaining the deer 

 problem, because no deer have ever been found fossil in Africa 

 south of the Sahara, and those species which have succeeded in 

 establishing themselves in northern Africa have clearly done 

 so in recent geological times. Deer are absent from all the 



* Marsh, 0. C, " Introduction of Vertebrate Life in America," p. 36. 



t Matthew, W. D., "Osteology of Blastomeryx," p. 535. 



J Osborn, H. P., " Oenozoic Mammal Horizons," p. 88. 



§ Osborn, H. F., "Ten Years Progress in Palaeontology," p. 107. 



