1881. J ^^'^ rCope. 



Measurements. M. 



Length of free part of calcaneum 037 



Distal depth of the calcaneum 016 



-r^. ^ X -t e 1 (anteroposterior 0145 



Diameters cuboid face calcaneum -j ^ ^_^ 



I transverse 0145 



Length of navicular 008 



" cuboid 0145 



Transverse proximal width of three metatarsals 027 



T^. ^ „ -, . . ^ (anteroposterior 014 



Diameters of second metatarsal < '■ „„„ 



\ transverse 007 



Antero-posterior diameter of third metatarsal 0145 



-r,. , c e ^1 4. 4. 1 (anteroposterior 014 



Diameters of fourth metatarsal i „^„ 



I transverse 013 



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

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

 locality is the same as that which furnished the Triplopus cubitalis, the 

 AcJicehodon insolens, etc. 



HYRACODONTID^. 



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

 the single genus Hyracodon, 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. 



RHINOCERID^. 



This extensive family has left representatives in all parts of the Northern 

 Hemisphere, and species still exist in the Old World. From the following 

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



I. Four anterior digits. 



Incisors f ; canine ^ ; no horn ; posttympanic bone das,\\a.ci, Aceratherium. 



II. Three anterior digits. 



a. Posttympanic process not coossified with postglenoid. 



Incisors f ; canines f ; no dermal horn Uanop^ts. 



Incisors \ ; canines { ; no dermal horn Aphelops. 



Incisors f ; canines f ; no dermal horn Peraceras. 



Incisors { ; canines ^ ; a tuberosity for a dermal horn on each nasal bone. 



Diceratlierium. 



Incisors \ ; canines f ; a median dermal nasal horn (Jeratorhinus. 



Incisors f ; canines & Zalabis. 



Incisors f ; canines ^ ; dermal horn median ; no osseous nasal septum .... 



Atelodus. 



aa. Posttympanie process coosified with postglenoid ; 



Incisors \ ; canine °- ; dermal horn median ; nasal septum not ossified 



BJiinocenis. 



Incisors § ; canine g ; dermal horn median ; nasal septum ossified 



Coelodonta 



