TKIPLOPUS. 691 



Length of inner malleolus - 007 



Length of astragalus on inner side 030 



Depth of trochlea on inner side 017 



Depth of head on inner side 0145 



Width of trochlea 015 



Width of navicular facet 0195 



Length of head from inner crest of trochlea ._. 005 



Length of calcaneum - 058 



Length of free part of calcaneum 037 



Distal depth of the calcaneum 016 



Diameters cuboid face calcaneum ^*"t«'-°P°«t«"°'' °J*^ 



< transverse 0145 



Length of navicular 008 



Length of cuboid - 0145 



Transverse proximal width of three metatarsals 027 



Diameters of second metatarsal < ^ _., 



c transverse W7 



Antero-posterior diameter of third metatarsal 0145 



Diameters of fourth metatarsal < ^ „,„ 



( transverse "i* 



This species was obtained in 1873 from the bad lands of South Bittei' 

 Creek, Wyoming, from the Washakie basin of the Bridger formation. The 

 locahty is the same as that which furnished the Triplopus cuUtalis, the 

 Achcmodon insolens, etc. 



HYRACODONTID^. 

 This family, which I characterized in 1879, includes, so far as yet 

 known, the single genus Hi/racodon, which is found in the Oligocene White 

 River formation of North America. According to Marsh, the digits of this 

 genus number three on both anterior and posterior limbs. It has a full 

 series of incisor teeth in both jaws. 



RHINOCERIDiE. 



This extensive family has left representatives in all parts of the North- 

 ern Hemisphere, and species still exist in the Old World. From the fol- 

 lowing table the range of variation of its genera can be readily seen: 



I. Four anterior digits. 



lucisors f ; canine f ; no horn ; postt ympanic bone distinct Aceratherium. 



II. Three anterior digits. 



a. Posttympanic process not coossifled with postglenoid. 



Incisors f ; canines f ; no dermal horn Cwnopus. 



Incisors \; canines ^; no dermal horn Aphelops. 



Incisors f ; canines ^; no dermal horn Peraeeras. 



