406 LAND MAMMALS IN THE WESTERN HEMISPHERE 



already referred to, was due to an actual geographical differ- 

 ence in contemporary faunas, or whether it is merely one of the 

 accidents of preservation and collecting. In the upper White 

 River, however, was another most curious animal (^Protoceras), 

 a forerunner, if not a direct ancestor, of ]Syndyoceras. The 

 exact relationship between the two forms can hardly be de- 

 termined, until the genera, one or more, which once connected 

 them shall have been recovered, though it is obvious that they 

 belonged to the same series. \Protoceras was a smaller ani- 

 mal and, if anything, an even more bizarre-looking object, for 



Fig. 217. — ^Protoceras celer, skull of male. (After Osborn and Wortman.) 



the anterior protuberances were broad, prominent and everted 

 plates of bone, not even suggesting horns in their form, and 

 the posterior pair were short and club-shaped ; in the female 

 neither pair was more than indicated. The dentition was very 

 similar to that of ^Syndyoceras, except that the upper tusk 

 was considerably larger and scimitar-shaped ; the female had 

 no tusks. In the fore-arm the two bones were just beginning 

 to coalesce, but in the lower leg the fibula was completely 

 reduced. The manus had four complete and functional digits, 

 the laterals not very much shorter and thinner than the median 

 pair ; but the pes was already didactyl, though the metatarsals 

 were separate, not fused into a cannon-bone ; two long and 



