1912] 



Merriam: Carnivora of R< 



'audio La Brea 



41 



Ursus the posterior articular faces of the atlas commonly extend 

 backward on angular processes which project some distance 

 behind the proximal region of the posterior border of the trans- 



Pig. 3. Arctotherium simum Cope. Atlas, superior view. No. 3035, 

 X 1 /:!. Pleistocene of Potter Creek Cave, California. 



verse process. In Arctotherium the posterior border of the 

 transverse process is slightly notched, but the plates supporting 

 the posterior articular faces are not as prominent as they may 

 be in Ursus, and there is a very narrow posterior notch. In 

 both of the characters just mentioned atlas no. 12786 from 

 Rancho La Brea is distinctly ursine rather than arctotherine. 



The atlas may be referred to the genus Ursus, but specific 

 determination is hardly possible with the material available. In 

 form, size, and position of the posterior opening of the verte- 

 brarterial canal the atlas specimen from Rancho La Brea is 

 nearer to the black bear than it is to the grizzly. The form of 

 the transverse processes differs somewhat from both black and 

 grizzly. Unfortunately in the fossil specimen these processes are 

 incomplete on both sides, and no distinctive characters can be 

 based upon them. 



The animal represented by the ursine atlas from Rancho La 

 Brea was about as large as a grizzly of average size, but was 

 very considerably smaller than the gigantic Arctotherium cali- 

 fomicum known from these beds. 



Measurements of Atlas 



Least anteroposterior diameter on dorsal side 



Greatest transverse diameter across anterior articular faces 

 Greatest height of neural canal 



65.5 



25.3 mm. 



26. 



