1919] Merriam: Tertiary Mammalian Faunas of Mohave Desert 511 



internal fold is more prominent on both P 3 and P 4 in M. rusticus than 

 in the Barstow species. The internal cingula are strong on the pre- 

 molars. The external cingula are fairly marked. The lower molars 

 have moderately elongated crowns on the specimens available for 

 study. There are faint internal ribs on the metaconid and entoconid 

 columns. 



A single astragalus, no. 21486 (fig. 89), from the Barstow may 

 represent an oreodont form. 



Measurements of Skull and Dentition 



No. 21350 No. 21485 



Length, anterior side of superior canine to posterior side 



of M 3 142 mm 



Length of superior molar-premolar series 128.5 



Length of superior premolar series 53.5 



Length of superior molar series 75 



1 2 , greatest transverse diameter 5.3 



1 3 , greatest transverse diameter 7.4 



Superior canine, greatest transverse diameter 14.7 



P 1 , anteroposterior diameter ol2.2 



P 2 , anteroposterior diameter 15.8 



P 2 , transverse diameter 10.5 



P 3 , anteroposterior diameter 14.8 



P 3 , transverse diameter 14 



P 4 , anteroposterior diameter 13 12.8 



P 4 , transverse diameter 17.8 16.4 



M 1 , anteroposterior diameter 19.6 15 



M\ transverse diameter 22 20.6 



M 2 , anteroposterior diameter 26.3 24 



M 2 , transverse diameter 26.4 24 



M 3 , anteroposterior diameter 34.5 29.7 



M 3 , transverse diameter 27.8 30.7 



No. 21354 



P 2 , anteroposterior diameter 12.8 



P 2 , transverse diameter 6 



P 3 , anteroposterior diameter 15.5 



P 3 , transverse diameter 10.4 



P 4 , anteroposterior diameter 17.2 



P 4 , transverse diameter 12.1 



No. 21487 No. 21485 



M 2 , anteroposterior diameter 24.8 a24 



M., transverse diameter 16.1 al6 



M ; , anteroposterior diameter 37.2 38 



M 3 , transverse diameter 13.2 17.2 



a, approximate. 



