NO. 8 UPPER EOCENE ARTIODACTYLA — GAZIN 79 



Discussion. — As has been noted in the previous discussion, discovery 

 of such a form as Poebrodon has been long anticipated. The most 

 significant information to come from this find, however, is the demon- 

 stration that the Uintan stage of development is strikingly Poehro- 

 therium-Wke. Except for the more-brachydont teeth and only slightly 

 more-noticeable styles of the molars, Poebrodon is scarcely more than 

 a very small Poebrotherium. The upper molars of Poebrodon do 

 resemble Leptomeryx, but the parastyles and mesostyles are more 

 compressed, the ribs flatter, and the transverse width of the teeth, 

 particularly of M^, is very much less. Moreover, there is evidence for 

 a very strong posteriorly directed style from the metacone of M^. 



The poebrotherine character of the lower molars is possibly even 

 more striking. The lingual wall of these teeth, however, is somewhat 

 less flattened, as noted in the slight flexure in early wear at about the 

 position of a metastylid, and in the somewhat more emphasized bilo- 

 bate appearance resulting from convexities about the metaconid and 

 entoconid, respectively. Nevertheless, the anterior and posterior 

 columns of these teeth, as in Poebrotherium, are more distinctly 

 separate from one another than, for example, in the leptomerycids. 

 This efifect of separate columns results from the early union of the 

 flattened metaconid with the anterior and posterior crests of the proto- 

 conid, and similarly the union of the hypoconid crests with the ento- 

 conid. The important poebrotherine distinction lies in the deflection 

 of the anterior crest of the hypoconid inward and away from the 

 posterior crest of the protoconid and its joining instead with the 

 entoconid. The two columns are thus joined only along the lingual 

 wall. In these respects the Poebrotheriinae are distinct from the 

 leptomerycids and differ fundamentally from the oromerycids. 



POEBRODON KAYI,43 new species 



Plate 15, figure 3 



Type. — Left maxillary fragment with M^, M^, and most of M^, 

 U.S.N.M. No. 20393. 



Horizon and locality. — Uinta C, Myton pocket, Uinta Basin, 

 Duchesne County, Utah. 



Specific characters. — Teeth a little less than one-half the size of 

 those in Poebrotherium wilsoni. 



Discussion. — In addition to the type upper dentition there are in 

 the collection two portions of a left mandibular ramus, U.S.N.M. 

 No. 20392, including M3, Mg with entoconid portion broken away, 



*3 Named for Dr. J. LeRoy Kay. 



