FREE INSTITUTE OF SCIENCE 



49 



UINTA SELENODONTS 



uals, no indication is given as to which should be regarded as the type. In 

 view of these doubtful matters, the question as to the synonomy of Parameryx 

 and Leptotragidus is not even yet altogether clear. 



The dentition of Leptotraguhis is still quite imperfectly known, but it 

 may readily be distinguished from that of any other Uinta selenodont ; it is, 

 on the whole, most like that of Protylopus, but differs markedly from the 

 latter in the presence of a long diastema in front of p-g- and in the large 

 caniniform tooth in the mandible. It is still a matter of considerable uncer- 

 tainty whether this caniniform tooth is a transformed premolar or the true 

 canine, because in no specimen yet found is the crown of this tooth or of 

 the incisors preserved. However, the course taken by the fang and the 

 shape of the remnants of the crown render it more likely that the tooth is 

 a true canine. In this case the number of inferior premolars is reduced to 

 three. The other mandibular teeth very much resemble those of Protylopus, 

 and thus are easily to be distinguished from those of Leptoreodon and the 

 other contemporary genera. 



The caniniform tooth is large, erect, and slightly recurved, its fang run- 

 ning upward and forward; so much of the crown as is preserved is of com- 

 pressed oval section. As already mentioned, the number of lower premolars 

 is perhaps reduced to three through the loss of the first, though better pre- 

 served specimens than any which have yet been found may show p T to be 

 present and caniniform. Between this tooth and p ? is a considerable dias- 

 tema, much as in Leptoreodon. The second premolar is a much compressed, 

 simple cone, with acutely pointed apex and trenchant edges, and having no 

 accessory cusps of any sort; in its antero-posterior elongation it resembles p^ 

 in Protylopus rather than that of Leptoreodon. The third premolar has a 

 crown of similar form, but is provided with a minute antero-internal basal 

 cusp, and on the posterior half is a low internal ridge, which encloses a very 

 narrow fossette, almost exactly as in Protylopus. The fourth premolar is 

 hardly at all larger than the third, which it resembles, except for the larger 

 size of its accessory elements ; it has a high and very sharply pointed princi- 

 pal cusp (protoconid) and a small, acute, anterior basal cusp, which arises on 

 the inner side of the crown. From the apex of the protoconid a thin ridge 

 runs downward and backward, enclosing a narrow, deep fossette between 

 itself and the outer wall of the crown. Protylopus has an extremely similar 

 p^, but the anterior basal cusp is smaller and so completely internal as hardly 

 to be visible from the outer side. 



4 



