27 



Length of upper third preinohir 015 



Width of upper third premolar 0194 



Lengtli of upper fourtli premolar 013 



AVidth of upper fourtli premolar, about 018 



Length of upjier first molar 0135 



Width of upper first molar OIT.'J 



Length of upper second molar, about 013 



"Width of upper second molar, about 0163 



Length of upper third molar 0135 



Width of upper third molar 017 



Lower jaw. — The incisors are nearly uniform in size and are semi- 

 procumbent. There is no disastema between the incisors and canine; 

 but the one between the canine and the first premolar is much longer 

 than in A. equinum, both relatively and actually; and the canine is 

 proportionately higher, projecting high above the grinding surface of 

 the incisors. The symphysis is very long. The alveolar border is ele- 

 vated above the anterior border of the jaw. The first premolar is a 

 small, simple, fiattened, subconical tooth. In the second premolar 

 there is a slight valley on the anterior-external side. The tooth is a 

 little more worn than in the specimen of A. equinum figured by Scott, 

 but is nearly of the same shape. The other premolars and molars are 

 also of nearly the same form. 



MEASUREMENTS. 



M. 



liCngth of mandible to molar 3 Ill 



Width of second lower incisor 0055 



Length of third lower incisor, about 0055 



Length from canine to premolar I, between alveoli 0325 



Length of premolar series 0-145 



Length of lower first premolar 000 



\\'idth of lower first premolar 00:52 



Length of second lower premolar 0130 



Width of lower second premolar 0077 



Length of lower third premolar 013 



Width of lower third premolar 0005 



lyength of lower fourth premolar 012 



"Width of lower fourth premolar 0103 



Length of lower first molar 01(i8 



Width of lower first molar 0097 



I^ength of lower second molar 0100 



Width of lower second molar <I0'» 



Both the above specimens were foimd in tiie Tyoup Fork formation in 

 tlif lower ^Fadison vallev. 



