in; 



University of California Publications in Geology [Vol.10 



M7, the only representative of the lower cheek-tooth dentition, is 

 unfortunately so much worn that it illustrates comparatively few 

 characters of the tuberculation (fig. 13). It is distinguished from 

 the corresponding element in the dentition of Hyaenarctos and of 

 certain forms of Arctotherinm by the relative proportions of the 

 trigonid and talonid regions. In the Oregon specimen the antero- 

 posterior diameter of trigonid and talonid are, as nearly as can be 

 determined, approximately equal. In Hyaenarctos, as is indicated by 

 the measurements below, the talonid may have an anteroposterior 

 diameter near one-half that of the trigonid. In Arctotherium simum 

 the functional talonid may be longer than the trigonid. In some of 

 the South American arctotheres, as in Pararctotherium enectum 



Fig. 13. Indarctos(P) oregonensis, n. sp. Mj, no. 22362, occlusal view, natural 

 size. Rattlesnake formation, John Day Valley, Oregon. 



Fig. 14. Hyaenarctos punjdbiensis ? Lydekker. Mj, occlusal view, natural 

 size. Siwalik beds, India. (After Lydekker.) 



Ameghino, the proportions are as in A. simum; in others, as in A. 

 triiu/ti Ameghino. the talonid is relatively short. The increase in 

 length of the heel region in A. simum is evidently related to the 

 increase in area of M-, as the talonid of articulates with the 

 trigonid portion of M-. 



The tuberculation of ^Sl-, represents only the inner side of the 

 tooth, on which is shown the relatively high region occupied by the 

 metaconid, and the lower more or less basin-like talonid region. The 

 talonid possessed a rather wide hypoconid ridge, and two smaller cusps 

 on the inner border a.s in Hyaenarctos. 



The crown of M 5 is supported upon two roots of which the posterior 

 is the larger. 



13 



14 



