90 University of California Publications in Geology [Vol. 10 



below the top of the rhyolite cap which forms the summit of the 

 section at the type locality of the Rattlesnake. 



The material representing the Pliocene bear includes the most 

 important parts of the dentition, with six or seven representative 

 elements of the limbs. There is good reason for considering that all 

 of these specimens are derived from one individual. The preservation 

 of the bones and teeth corresponds in general to that of other mammal 

 remains obtained in the type section of the Rattlesnake formation. 



DENTITION 



The dentition of specimen no. 22362 from the Rattlesnake Pliocene 

 includes practically all essential elements. Prom the upper jaws there 

 are represented P, P, C, P-, and M-. The first upper molar is 

 the only superior tooth of importance lacking. Prom the mandible 

 only the canines and were found. "While it is to be regretted that 

 the lower earnassial is not available, it should be noted that the forms 

 most nearly related to this particular type show less variation in M T 

 than in P-, M-, and Mtt, all of which are at hand. The teeth present 

 illustrate so fully the characters of the dentition as a whole that it 

 is possible to make those comparative studies most important in 

 determination of the relationships of this animal. 



The two upper incisors present are much worn. So far as 

 can be determined, they are of approximately the type seen in 

 Arctothcrium, lint are larger than the corresponding elements in A. 

 simum of the California Pleistocene. 



Figs. 1 ami 2. hidarctosf ?) oregonensis, n. sp. Canine teeth, no. 22362, lateral 

 view, X Vo. Fig. 1, upper canine; fig. 2, lower canine. Rattlesnake formation, 

 John Day Valley, Oregon. 



