TIIK MAMMALIA OF THK UINTA FORMATION. 419 



AKTIODACTYLA. 



LEPTOTRAGULUS S. & 0. 



Our pieliminaiy account of this genus was founded upon the mtindible and infe- 

 i-ior dentition. Since then a considerable amount of new matcnal has been brought 

 to light in the collection which mateiially modifies some of our conclusions. The 

 genus may be thus defined: Selenodont artiodact^'ls with probabl}"^ unreduced den- 

 tition; lower premolars simple and ti'cnchant ; molars with short crowns; the cres- 

 cents of the lower molars are more or less trihedral, and the internal ones not flat- 

 tened into thin lamina?. The ulna and radius closely applied, but not coalesced; the 

 number of functional digits in the manus probably four, in the pes two. 



Leptotkagulus pkoavus S. & O. (PI. VII, Figs. 9-1(5). This species, the only 

 one as yet certainly indicated fi-om the Uinta deposits, is represented in the collection 

 by sevei-al specimens, including the mandible, inferior molar series and last premolar, 

 some fragments of vertebra3 and portions of the humerus, ulna and radius, metacai- 

 pus, phalanges, scapula, tibia, tai'siis and metatarsus. Imperfect as these remains 

 are, they suffice to show the principal characters and systematic position of the 

 genus with sufficient clearness. Unfortunately no part of the skull or of the upper 

 teeth has as yet been identified. 



The Mandible. Only the horizontal ramus is pi-eservcd in any of the specimens; 

 this is elongated, compressed and slender, becoming especially thin beneath the ante- 

 rior premolars, and thus offering a strong contrast to the short deep mandible of /*ro- 

 toreodon with its abrupt chin. The symphysis extends back nearly as far as the 

 front of the second premolar; two minute venous foramina are placed, one above the 

 other, beneath the third premolar. 



Dentition. The fraguientary state of the specimens prevents the determination of 

 several important points with refeience to the lower teeth of this genus. Thus, the 

 number and character of the incisors and canines are altogether uncertain, though [nob- 

 ably they were present in lull. In front of the third ()remoIar is a short diastema, and 

 in advance of this occurs a pair of oblirpiely placed alveoli, which may have contained 

 the first premolar, or the canine and lateral incisor, which latter view seems the more 

 probable on account of the procnmbency indicated, though this would necessitate an 

 exceedingly short symphysis. In this case, the number of lower premolars would be 

 but three. The premolars ai-e very simple and trenchant, and in general appearance 

 quite like those of IViif/ulus. Pm. 2 has a very compressed and sh'.irjjly trenchant 

 crown; it has a sharper posterior edge than in Traf/ul us ixnd is ap|)arontly not divided, 

 as in that genus, by a cleft. Of pm. 3 only the fangs are left. Pm. 4 is slightly 



