Cope.] dOO [Feb. 19, 



do not display any material differences from those of the J., longieriste. 

 The premolars and molars have a well- marked external cingulum, 

 and there is an internal cingulum round the base of the second pre- 

 molar. The only other cingula are weak ones round the bases of the 

 anterior lobes of the second and third true molars. The anterior inter- 

 mediate tubercle forms an angulation in the outline of the anterior 

 cross-crest of the premolars, and a rounded enlargement in that of 

 the true molars. The posterior intermediate tubercle has a triangu- 

 lar section. The anterior teeth are curiously unsymmetrical. There 

 are six incisors, the third having a more posterior position on one side 

 than on the other, and having a cupped crown. The crowns of the 

 others are lost. On the right side, behind a diastema rather longer than 

 the transverse width of the crown of the third incisor, is a robust canine 

 tooth. On the opposite side there is no canine tooth, nor a trace of one 

 ever having been there. The diastema separating the canine from the first 

 premolar is long. The latter has but one root and has a rather small 

 crown. 



It is in the cranial characters that this species displays the greatest dif- 

 ferences from the John Day species. In the first place there is a profound 

 and large preorbital fossa, separated from the orbit by a vertical bow. The 

 preorbital fossa in the John Day species is shallow, and not abruptly 

 defined. In the next place the anterior border of the orbit is above the 

 anterior border of the last molar tooth. In this it agrees only with the 

 large A. prastans ; in the A. cquiceps and A. longieriste, the anterior border 

 of the orbit is above the anterior part of the second superior molar. 

 Thirdly, the infraorbital foramen is above the middle of the fourth premo- 

 lar ; it is over the posterior part of the third in the three John Day spe- 

 cies. Finally, the nareal notch marks the anterior two-fifths of the dias- 

 tema ; it extends much further back in the John Day species, marking 

 either the front or middle of the first premolar. The palate extends about 

 as far anteriorly as in A. prcestans, viz., to opposite the posterior border of 

 the first true premolar. 



Measurements. M. 



Length of diastema from I. 3 047 



" " '* " C, 085 



" " superior molar series 079 



" " " true molars 034 



" " crown of p. m. 1 (greatest) 007 



Diameters of crown of p. m. ii -[ anteroposterior 0145 



t- transverse 0145 



,, ,, ,, ,, • f anteroposterior Oil 



I transverse 015 



in. 



t anteroposterior 011 



I. transverse 014 



Long diameter of crown of I, 3 007 



Depth of muzzle at middle of diastema 039 



