112 ORIGIN OF LIFE IN AMERICA 



as well as the nature of the land bridge which enabled the 

 deer to reach western America rather than the east, will be 

 discussed in one of the subsequent chapters. Some of the 

 more primitive forms still survive in South America, where 

 they have now been pressed into the mountain regions. The 

 newer and more vigorous types must have passed into North 

 America as soon as that continent became definitely connected 

 with South America in later Tertiary times. 



In speaking of the western North American fauna, Pro- 

 fessor Osborn * tells us that in middle Miocene the peculiarly 

 American Hypertragulidae disappeared, while the European 

 Cervidae and the distinctly American Merycodontinae took 

 their place. Professor Osborn alludes no doubt to Palaeo- 

 meryx and Blastomeryx which seem to have originated in 

 southern Europe, and spread subsequently eastward to India 

 and onward to America. Both apparently became extinct in 

 North America before the advent of Odocoileus from the 

 south. 



The other large hoofed animal I alluded to as frequenting 

 the lower slopes of the Rocky Mountains is one of the most 

 peculiar creatures in existence. It is so different from other 

 animals that it occupies the exclusive position of being the 

 solitary member of a distinct family. Known among zoo- 

 logists as the "prong-horn" (Antilocapra americana), and 

 among hunters as the " antelope," this splendid animal 

 possesses the graceful movements of the latter, while its horns 

 have a superficial resemblance to the antlers of a deer. There 

 is not the least real likeness, however, between the antlers 

 of the prong-horn and those of a deer, for they are not solid, 

 but hollow like the horns of a goat. The horn -sheaths,, 

 like the antlers of a deer, are shed and reproduced at regular 

 intervals. The prong-horn ranges from eastern Mexico to 

 Saskatchewan in Canada and from the Missouri River in the 

 east to the Cascade Mountains of Oregon in the west. Hence 

 it is now a peculiarly western species, while it had crossed 

 the Mississippi during the Pleistocene Period, and roamed 

 about Illinois and Wisconsin. The closely-allied extinct 

 genus Merycodus (Cosoryx) made its first appearance in the 



* Osborn, H. F., " Cenozoic Mammal Horizons," p. 77. 



