NO, 8 UPPER EOCENE ARTIODACTYLA — GAZIN 49 



Leptoreodon, as noted by Wortman, comes close in the general 

 structural plan of upper dentition, but the anterior extension of the 

 snout as well as other skull characters would seem to preclude this 

 genus, and I particularly note that the lower premolars, especially P4, 

 present greater difficulties than Protoreodon. The lower premolars 

 of Leptotragulus, on the other hand, as exemplified by L. medius, 

 would appear potentially close. In both Leptoreodon and Lepto- 

 tragulus the lingual portion of the upper molars and the labial portion 

 of the lower molars satisfactorily meet the requirements. The primary 

 cusps, outer above and inner below, however, are decidedly more 

 conical than in Merycoidodon; a condition that might be expected 

 in a somewhat more remote ancestry of the highly crescentic pattern 

 of Merycoidodon. I believe that the gap is rather significant and that 

 the dental indications are for a closely related common ancestry rather 

 than direct sequence. Clearly a compromise form is needed, exhibiting 

 the paramerial form more as in Protoreodon and the protomerial 

 structure of Leptotragulus or Leptoreodon. 



PROTOREODON PUMILUS 22 (Marsh), 1875 

 Plates 4, 5, and 6, figure 2 



Synonyms. — Protagriochoerus annectens Scott, 1899. 

 Protoreodon medius Peterson, 1919. 

 "^Protoreodon tardus Scott, 1945. 



Type. — Lower jaw fragments with Mi and portions of M2 and M3 

 from right side and M2 from left, including also various other skeletal 

 fragments of Y.P.M. No. 11890, 



Horizon and locality. — Vicinity of White River, Uinta Basin, Utah, 

 probably Uinta C according to Thorpe. 



Discussion. — Although Thorpe lists Y.P.M. No. 11890 as a cotype, 

 I believe it should be regarded as the holotype, and is here so desig- 

 nated, inasmuch as the maxillary portions and upper molars belong- 

 ing to Y.P.M. No. 11890a were referred to by Marsh (1875) as the 

 "second specimen." It is interesting to note that neither of these 

 specimens was figured and that the skull, Y.P.M. No. 11891, and 

 jaws, Y.P.M. No. 10570, illustrated by Marsh in 1894, among the 

 materials that he obtained "by subsequent researches in the Uinta 

 basin," ^^ may not represent Protoreodon pumilus as they appear to 

 be closer to Protoreodon parvus. 



22 Illustrated also in Scott, 1899, pi. 4, figs. 26-27; 1945, pi. 2, figs, i, la; pi. 3; 

 Peterson, 1919, fig. 13; pi. 40, figs. 1-16, 19-27, and pi. 41; and Thorpe, 1937, 

 fig. 8; pi. I, fig. I. 



23 As an aside on the record of collections, Marsh (1894) claimed that the 



