40 University of California Publications in Geology [Vol. 7 



t 



Ursus, sp. 



The remains referred to Ursus consist of an atlas (no. 12786) 

 and fragments of other vertebrae. The atlas (figs. 1 and 2) is dis- 

 tinctly of the ursid type. It resembles Ursus, and differs from 



Arctotherium in the character of the posterior opening of the 

 vertebrarterial canal. The general form of the transverse pro- 

 cess seems also to resemble Ursus more closely than Arctotherium, 

 although this cannot be demonstrated as the ends of these pro- 

 cesses are broken away. 



In such material as is available for comparison the atlas of 

 Ursus differs from that of Arctotherium in the location of the 

 posterior opening of the vertebrarterial canal. In Ursus this 

 opening is on the upper side of the posterior face of the trans- 

 verse process; in Arctotherium (fig. 3) the posterior opening is 

 on the upper side of the transverse process some distance in 

 advance of the posterior margin, much as in the Canidae. In 



