548 



THE MAMMALIA OF THE UINTA FORMATION. 



examination.* The diagnostic features of the members of the Htjracliyus series are 

 the relatively flat or obtuse keels of the trochlea and the frequent confluence of the 

 snstentacular and inferior calcaneal facets of the astragalus. The same facets are 

 invariably separate in the equine series, beginning with Ilyracotherium. The Hijra- 

 chyus calcaneum occasionally shows a pit for the fibula, but this does not bear a facet 

 as in nearly all the equine series. 



ra.lonZ' 



H/ra^chr 



Trinlon- 



Hyra^cod- 



DiAO. 11. — The astragalar and calcaneal facets in the nyracUyus-IIyracodon series. Paloplotherium minus, 

 Princeton collection. IJyrachyus (sp. inilet.), Princeton collection. Triplopus ohliquidena, Princeton collection. Hyra- 

 codoii major, Princeton collection. 



Hyrachyus (No. 10,199, Princeton Coll.). The cuboidal contact with the 

 astragalus expands j)osteriorly, but is very narrow anteriorly in some species 

 {H. j)rinceps\ bringing the navicular into contact with the calcaneum precisely as in 

 some species of Ilyracotherium {Triplojms amarm'um) ; as above stated there are 



* I liavc referred the Triplopus amarorum of Cope, from the Washakie beds (uppermost Bridger), to the eijuine 

 series. 



