TllK MAMMALIA OF THE UIN'TA FOiniATIOy. 525 



from the Bridfjer, that it is i)Ossihlc' that some of the hvtter belong to Trlplopia. As 

 Cope has pointed out, this genus is near the J/t/rachi/us-IJi/racodon series, as shown 

 by the teeth and the reduced condition of the fifth digit. It was an extremely light 

 and graceful animal, with long skiulcr limbs and feet of the proportions seen in 

 Jifesohipjnis, and about the height of tlie smaller domestic sheej). The manus and 

 pes are extremely elongate, the podials being hiterally compressed, the metapodials 

 spreading very little, much less apparently than in either IlyracJn/us or Jlijracoihut. 

 The peculiarity of the manus is that the lunar rests almost entirely upon the unci- 

 form anteriorly. In the pes the cuboid is elongate and articulates with the astragalus 

 by a very narrow joint. The genus is distinguished from Hijrachyus by the Hatten- 

 ing of the external molar crests and their backward extension, also by the advanced 

 reduction of mc. v. From Ilelaletes, by the single internal lobes of the i)remolars 

 3 and 4. There is a wide diastema behind the canine and the last lower molai- is 

 without a third lobe. 



This genus is represented in our collection by jxirtions of five or more individu- 

 als ; in every case the specific determination is uncertain and the generic reference of 

 one specimen is somewhat doubtful. The t\'pes include the Prollniracodon hdenne- 

 diitm (Xo. 10,40.'3) and IluracJn/us ohiiquidens (No. 10,402) of our preliminary bul- 

 letin. The former type, together with several individuals which are represented by 

 skeletal fragments, is nosv referred to the same species as the latter; the latter, a 

 superior molar, m.", evidently belongs to Trqdojms, and has associated with it a lower 

 jaw which either lacks or has a rudimcntal first premolai', a good specific distinction 

 from T. cuhitalis Cope. The type of P. intermedium cannot be distinguished from 

 T. cuhitalis, except by indirect association with the T. ohliguiden.s type. 



Generic characters. Denlit ion, i. [!, c. ], pm. ;| I, ra. if A diastema behind the 

 canine. Fourth and third premolars submolai'iform ; upper third and fourth pro- 

 molars with single internal lobes. External crests of superior molars llatlened. 

 Third lower molar bilobed. S k u 1 1, meatn^ nn/litoriiis e.vternus closed by bone infe- 

 riorly. Tymj)anic expanding into a bulla. Posttympanic and paroccipital processes 

 distinct. No postorbital arch. Manus and pes. Digits 3-3. Fifth metacarpal 

 rudimental. Lunar resting principally upon unciform. Astragalus with slight 

 cuboidal contact. 



.TniPLorus obliquii>en.s S. A: O. 



I'l.ATK XI. 



7'. olifit/uiden^s. Syn. : fli/rdc/n/ns ithlit/xidens, nobi.s, Proc. Am. Phil. Soc, .^ept., 

 18S7, p. 2.^0; probal)ly also, Protlniriicitdmi. int-rnifdiuin, nobis, /oc. ''/V., p. 2(30. 



A. !■. S. VOL. XVI. 3o. 



