1881.] 393 [Cope. 
. Measurements. M. 
Length of free part of caleaneum...............0.0000. 037 
Distal depth of the caleaneum................0.0000 00. .016 
Diameters cuboid face caleaneum { BEN ERS POR IERIOE: asi wes 
transverse.......... .0145 
Length of navicular...... iA eusas aoe cameos «s+. 008 
s CUDOM p2aceves acy daaee deere ad cae seoeeee 00145 
Transverse proximal width of three metatarsals ........ 027 
Diameters of second metatarsal { ET ODE ACT Pe ates ont 
transverse...... see 007 
Antero-posterior diameter of third metatarsal........... .0145 
Diameters of fourth metatarsal bacon Phe hag Le 
transverse............ .012 
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 
Achenodon insolens, etc. 
HYRACODONTID &. 
This family, which I characterized in 1879, includes, so faras 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 2; canine 9; no horn; posttympanic bone distinct, Aceratherium. 
II. Three anterior digits. 
a. Posttympanic process not coéssified with postglenoid. 
Incisors ?; canines 2; no dermal horn ............ceeeeee eens Cenopus. 
Incisors }; canines 2; no dermal horn........... Rees asses Aphelops. 
Incisors 2; canines 2; no dermal horn............ «+ eoeeeenne Peraceras, 
Incisors +; canines $; a tuberosity for a dermal horn on each nasal bone. 
Diceratherium. 
Incisors } ; canines 2; a median dermal nasal horn......... Ceratorhinus. 
Incisors 3; canines 9.......... 0c cee eee ee feed dataivee ese odes Zalabis. 
Incisors £; canines 2 ; dermal horn median ; no osseous nasal septum.... 
Atelodus. 
aa. Posttympanie process codsified with postglenoid ; 
Incisors }; canine 2; dermal horn median ; nasal septum not ossified.... 
Rhinocerus. 
Incisors ?; canine 3; dermal horn median ; nasal septum ossified........ 
Calodonta 
