Peterson: Material Discovered in Uinta Basin. 95 



Locality: Six miles east of Myton, Utah. 



Specific Characters: External faces of superior molars ivith relatively 

 large styles; cingula on superior molars absent. Species of approxi- 

 mately the same size as A. proavus. 



The premaxillaries and the front of the skull of the present type are 

 unfortunately lost. The upper dentition of this genus is therefore 

 not yet completely known. It is, however, \Ai\\n that there is a 

 diastema in front of P-. The latter is represented only b>- the two 

 roots. P- has three roots; in general features it is much as in Lep- 

 tomeryx of the Oligocene, except that the rib on the external face of 

 the protocone is somewhat less developed and the deuterocone is 

 smaller. P- is proportionately somewhat small, but with the excep- 

 tion of the smaller median rib on the external face and a slightly 

 smaller deuterocone, this tooth, as the preceding, is most nearly like 

 the same tooth in Leptomeryx. The main reason for separating this 

 species from Leptotragulus proavus is found in the larger external 

 pillars and the absence of the cingulum internally. The external 

 faces of both anterior and posterior external crescents have prominent 

 ribs as in Leptomeryx, and the internal faces are very nearly as vertical 

 as in the latter. The inner crescents have an equally perfect formation 

 as in the Oligocene genus, including the anterior and posterior cingula 

 and the slight indication of the minute median tubercle. The chief 

 difference between the molars of Leptotragulus and Leptomeryx are 

 the greater brachyodonty and proportionally smaller size of M^ in 

 the genus from the Uinta. ^^ 



M3- of this species does not differ in any particulars from that in 

 L. proavus. From Leptomeryx of the middle Oligocene it differs by 

 being more brachyodont and by its narrower and simpler heel. 



The skull is so badly mutilated that it does not permit of an accurate 

 description. It is, however, possible to determine that the occipital 

 plate is rather narrow, that there is a long and quite decided sagittal 

 crest. The temporal crest is well defined and terminates in a promi- 

 nent post-orbital process. The orbit is large, its anterior border; is 

 directly above the posterior portion of M- as in Leptomeryx or Ilyper- 

 tragulus, but is probably widely open posteriorly. The alveolar 

 portion of the maxillary is rather high for an animal with brachyodont 

 teeth, but in this respect it is also like the Oligocene genera Leptomeryx 



55 This comparison is based on the type specimen of Leptomeryx iransmontanus 

 Douglass from the Upper Ohgocene of Montana. 



