HISTORY OF THE ARTIODACTYLA 365 



the molar-pattern. If the feet and hmbs of this upper Miocene 

 peccary were known, they would doubtless prove to be much 

 more primitive than those of Tagassu, but they still await dis- 

 covery. 



Little can be said of the peccaries of the middle and lower 

 Miocene other than to record the fact of their presence in those 

 formations, but those of the upper Oligocene (John Day) are, 

 however, represented by well-preserved skulls, which show that 

 more than one phylum of the family had arisen, though there 

 was no great difference between them ; they were considerably 

 smaller animals than those of the Pliocene and Pleistocene. 

 Still smaller was the White River genus ( jPerchoerus) of which 

 some fragmentary skeletons have been obtained. Although 

 an undoubted peccary, this animal was not far from what the 

 common progenitor of the peccaries and the true swine might 

 be expected to resemble. The molars were quadrituberculate 

 without the numerous accessory cuspules of the modern genus ; 

 the bones of the fore-arm were separate and the feet had four 

 functional digits each, while there was no cannon-bone in the 

 pes, the metatarsals remaining free. 



No peccaries have yet been found in the Uinta, but prob- 

 ably this is a mere accident of collecting. It is, however, 

 possible that the White River genus was not of American deri- 

 vation, but an immigrant from the Old World. In the middle 

 Eocene, or Bridger stage, this series is known only from teeth 

 and jaws and a very few scattered foot-bones, and these, 

 though probably referable to the family, cannot be definitively 

 assigned to it without more complete material. Several species, 

 larger and smaller, of the genus ^Helohyus occurred in the Bridger, 

 where they were not uncommon, considering the general rarity 

 of artiodactyls in that stage. Thus, the peccaries, though 

 none of them were large, followed the usual law of mammalian 

 development, and, beginning with very small forms, increased 

 in size with each succeeding geological stage down to the 

 Pleistocene. 



