NO. 8 UPPER EOCENE ARTIODACTYLA — GAZIN 6l 



as in Merycoidodon. I am unable to determine whether or not there 

 was a preorbital fossa. The sHght depression in this area on the type 

 specimen may be due to crushing on one side, and there has been some 

 restoration in plaster on the other. Of the remaining two skulls, one 

 is too crushed at this point and the other suggests that if there was a 

 preorbital fossa it was scarcely more than a very shallow depression. 

 Protoreodon petersoni comes nearer to being a possible ancestor of 

 Merycoidodon than any members of the P. parvus-P. pumilus line. 

 The modification of the paramere in molars of P. petersoni, unlike 

 the P. pumilus line, is not so distinctly in the direction of Agriochoerus 

 with rather small differences suggestive of Merycoidodon. P*, more- 

 over, has no tritocone, and the deuterocone tends to form a single 

 crescent. Nevertheless, the lingual portion of the upper molars and 

 the buccal portion of the lower molars are still agriochoerid in ap- 

 pearance. The posterior crest of the protocone is directed toward and 

 not parallel with the anterior crest of the metaconule, and the anterior 

 crest of the hypoconid is directed toward the posterior crest of the 

 protoconid so as to leave a distinct basin external or buccal to the 

 metastylid, quite unlike Merycoidodon. 



Genus DIPLOBUNOPS Peterson, 1919 



Type. — Diplobunops matthewi Peterson, 1919. 



Discussion. — Diplobunops appears to be a distinctive and valid 

 genus, although close to Protoreodon. It is characterized most notice- 

 ably by the somewhat lengthened rostrum, enlarged canines, and the 

 widely expanded anterior extremity in comparison with Protoreodon. 

 The premaxillae appear blunted forward with the third incisor 

 alveolus distinctly more median to the enlarged canine than in Pro- 

 toreodon. The rostrum is constricted posterior to the lateral expan- 

 sion of the maxillae over the roots of the canines, and P^ (in Uinta C 

 and later forms) is isolated by diastemata from the canine and P^. 

 P^ has a simple conical deuterocone with little or no tendency toward 

 the development of a posterointernal basin. In P* the primary cusp 

 in an unworn state does not appear to be twinned, but two generally 

 prominent ridges on the lingual side of this cusp converge toward the 

 apex so that moderate wear may produce the illusion of twinning. 

 The deuterocone on P* is comparatively conical although the antero- 

 laterally and posterolaterally directed crests are well defined. The 

 lower premolars, and the molars in both the upper and lower series, 

 are very much like those in Protoreodon; however, the molars are 

 distinctly less selenodont, buccally above and lingually below, than in 



