176 University of California Publications in Geology [Vol. 9 



California specimens. In comparison with the modern Bassariscus 

 astnta the fossil specimen (no. 19768) shows M x very slightly shorter 

 anteroposteriorly, and the mandible somewhat higher and thicker. In 

 the fossil form the posterior border of P 4 is less distinctly concave 

 and the posterior cusp is relatively a little less prominent. The 

 posteroexternal angle of the hypoconid of M. t in the fossil specimen is 

 more distinctly angular than in the Recent specimens of B. astuta 

 examined. 



A satisfactory comparison of the specimen from Stewart Valley with 



Probassariscus antiquus from 

 the Pliocene of Snake Creek, 

 Nebraska, and the Miocene of 

 Virgin Valley, is not possible, as 

 M 2 is absent. It may be that this 

 form possessed a paraconid on 

 the tuberclar molar as in Pro- 

 bassariscus, but this cannot be 

 determined until more material 

 is obtained. The mandible seems 

 noticeably heavier in Probas- 

 sariscus than in specimen no. 19768, and there is a slight difference in 

 the proportions of the lower earnassial. 



There can be little doubt that the Bassariscus form from the 

 Cedar Mountain region inhabited a territory that was fairly well 

 watered and partly wooded. The climatic conditions must have been 

 quite different from those obtaining in the Cedar Mountain region 

 at the present time. 



Measurements 



Fig. 10. Bassariscus nevadensis, n. sp. 

 Lower jaw with dentition, no. 19768, 

 X 2. Cedar Mountain beds, Stewart 

 Valley, Nevada. 



Cedar Mt. B. astuta 

 specimen (a) Recent (b) 



P 3 , anteroposterior diameter 4.3 mm. 



P,, transverse diameter 2.2 



P 4 , anteroposterior diameter 4.9 



P 4 , transverse diameter 2.4 



M,, anteroposterior diameter 7.1 



Mj, transverse diameter across 



metaconid 3.8 



M,, transverse diameter of heel-.. 3.2 

 M„ anteroposterior diameter from 

 base of protoeonid to pos- 

 terior end 2.4 



■ Depth of lower jaw below M„ .... 6.9 

 («.) No. 19768 (6) No. 8800 

 op, approximate. 



4.6 



2.3 



5. 



2.5 



7.3 



3.9 

 3.3 



2.4 



P. antiquus 

 B. astuta (c) matthewi (rf) 

 Recent Virgin Valley 



4.3 



2.2 

 5 



ap 2.4 

 7.6 



3.8 

 3.4 



5.2 

 2.7 

 6.8 



3.8 

 3.7 



2.4 

 6.7 



(c) No. 8799 



2.8 

 7.8 



(d) No. 12539 



