248 



University of California Publications. 



[Geology 



in either the Recent species or the form from the Snake Creek 

 Beds. 



P.. is represented only by alveoli of the two roots. P 4 is 

 slightly larger than in the modern B. astuta. The crown is not 

 satisfactorily shown, but the posterior cusp seems to have been 

 wider than in the living species. 



M t is unfortunately considerably worn, but is evidently 

 closely similar in form to the corresponding tooth of the living 

 species. The paraconid is possibly slightly thicker transversely, 

 or is turned so that its blade is more nearly transverse to the 

 anteroposterior axis of the tooth. 



M 2 differs from the corresponding tooth of B. astuta in its 

 relatively larger size, and in the presence of a distinct paraconid 

 ridge. Owing to the worn condition of this tooth it is not pos- 

 sible to determine exactly the stage of development of the para- 

 conid. A paraconid is also shown in the illustration of the type 

 specimen of P. antiquus from Snake Creek. The talonid region 

 differs from that of B. astuta in its greater width. The form 

 and position of the tubercles are much the same as in the Recent 

 species, excepting that the region of the entoeonid is more ele- 

 vated and is separated from the metaconid by a sharp fissure. 



The Virgin Valley specimen is certainly closely related to that 

 described by Matthew and Cook from the Snake Creek Beds. 

 In both forms the paraconid is present on M 2 , whereas it is 

 absent entirely in the living species. M 2 is also relatively large 

 compared with the inferior carnassial in both. 



Occurrence : Virgin Valley Beds, locality 1095, Virgin Valley, 

 Humboldt County, Nevada. 



Measurements 



Length, P 4 to M, inclusive 



Depth of jaw below M L 



P t , anteroposterior diameter 



My anteroposterior diameter 



Mj, greatest transverse diameter 



M 2 , anteroposterior diameter 



M 2 , greatest transverse diameter 



P. antiquus 

 matthewi 



17.6 mm. 



P. antiquus 



17.4 



B. astuta 



17.3 

 6.8 

 5. 

 7.5 

 3.7 

 5.2 

 3.2 



7.8 

 5.2 

 6.8 

 3.8 

 5.5 

 3.5 



7.9 

 3.8 

 5.9 

 3.5 



7. 



