HISTORY OF THE ARTIODACTYLA 



379 



tremely delicate a structure be preserved. In the John Day 

 the genus ^Eporeodon, which was very abundant, was the repre- 

 sentative of this phylum, and the same, or a closely similar, 

 genus lived in the latter part of the White River stage. 



In the middle and lower White River substages joreodonts 

 are the commonest of fossils, so that the collector soon wearies 

 of them (see Fig. 136, p. 259) ; they must have lived in great 

 herds in the forests and along the streams. There were several 

 species, varying principally in size, the largest about as long 

 as a wolf, but with shorter legs, and the smallest not so much 

 as half of that size. 

 All belonged to a single 

 genus, for which the 

 rigid law of priority 

 compels us to use a 

 most cumbrous name 

 ( ]Merycoidodon) , the 

 widely used term 

 ^Oreodon being a syno- 

 nym. This genus was 

 the central stock of the 

 family, from which 



most, if not all, the others were directly or indirectly derived, 

 though, as previously pointed out, we cannot in all cases trace 

 the connection. In these White River animals the grinding 

 teeth were very low-crowned and had considerable resemblance 

 to those of a deer; the molars were typically selenodont and 

 made up of two pairs of crescentic cusps. The skull differed 

 little from that of the succeeding genera of this phylum ; the 

 neck was short, body and tail long. An especially interesting 

 fact is that the fore foot had five digits, the first, or poUex, 

 very small and of no functional value, but complete in all its 

 parts ; the hind foot was four-toed. In all of the subsequent 

 genera of the family the number of digits was uniformly four 

 in both manus and pes. 



Fig. 202. — Skull of ^Merycoidodon culbertsoni, middle 

 White River. (After Leidy.) 



