HISTORY OF THE ARTIODACTYLA 421 



those that have yielded nothing. Certain broad outUnes of the 

 history may, nevertheless, be discerned. 



The suborder Pecora at an early date became divided into 

 the two great branches of the Cervicornia and Cavicornia, 

 the former giving off the giraffe series, which in the Miocene 

 and PUocene ramified and extended through Asia and southern 

 Europe, though now confined to Africa. In the lower Miocene 

 of Europe the muntjac-like deer and the antelopes, the first 

 of the Cavicornia, were already well distinguished. From the 

 primitive antelopes arose not only the wonderful assemblage 

 of modern antelopes, but also the goats and sheep and the great 

 and varied ox-tribe. From the middle Oligocene forms it 

 may obviously be inferred that both Cervicornia and Cavi- 

 cornia united in a single trunk, or, traced in the other direction, 

 diverged from a common stock, to which also the suborder of 

 the Tragulina goes back. 



On the other hand, it is equally obvious that the camels 

 and llamas have been separated from the Pecora at least since 

 the middle Eocene, and, consequently, the many points of 

 agreement between the two suborders, other than those shared 

 with all artiodactyls, are not due to inheritance from a common 

 ancestry, but have been independently acquired in the two 

 series. It will be instructive to note some of the more im- 

 portant of these independent similarities : (1) the selenodont 

 and more or less hypsodont character of the grinding teeth ; 

 (2) the spout-shaped odontoid process of the axis ; (3) the 

 great reduction of the ulna and its coossification with the 

 radius ; (4) the loss of the fibula, except for its lower end, which 

 persists as a separate malleolar bone ; (5) the formation of 

 cannon-bones by the fusion of the third and fourth metapodials ; 

 (6) the development of a complex, many-chambered stomach. 

 Other points of Ukeness might be cited, but those already given 

 will suffice to show how very important this parallel mode of 

 evolution often proves itself to be. 



