578 



University of California Publications in Geology [Vol. 11 



Measurements of Dentition — (Continued) 



No. 21351 



M 1 , anteroposterior diameter 28.3 



M 1 , transverse diameter 25.2 



M 2 , anteroposterior diameter 36.8 



M 2 , transverse diameter a31.3 



M 3 , anteroposterior diameter 45.5 



M 3 , transverse diameter a28.5 



«, approximate. 



Measurements of no. 21353, an Individual with Well Worn Teeth, 

 and M 3 Well Worn 



M 2 , anteroposterior diameter a27 mm. 



M 2 , transverse diameter a28 



M 3 , anteroposterior diameter 41.2 



M 3 , transverse diameter 33.2 



a, approximate. 



The dentition of the Ricardo oreodont shows an unusually long 

 molar series and relatively great length of this series compared with 

 the premolars. The length of the premolar series seems to be about 

 61% that of the molars, while in a Merycochoerus specimen available 

 for comparison the length is greater. In Leidy's type of M. proprius, 

 it is 85%. In the Pronomotherium specimens described by Douglass, 

 the length is 70% for P. laticeps, and 77% for P. altiramum. In 

 M. buivaldi from the Barstow beds the corresponding percentage is 

 71.3%. 



The whole assemblage of characters in the Ricardo specimen seems 

 to distinguish it as a member of the Merycochoerus group, and one of 

 the most advanced forms in the group. 



Comparative Measurements of Upper Molar and Premolar Series 



Length of Length of 



premolar molar 

 series series 



Merycochoerus proprius, type 68 mm. 80 



Merycochoerus buwaldi 53.5 75 



Merycochoerus? calif oruicus* 63.5 104 



Pronomotherium laticeps 56 80 



Pronomotherium altiramum 70 90 



* In MJ calif ornicus the molar and premolar dentition are not completely 

 represented in one specimen. 



Compared with Pronomotherium altiramum the Ricardo form 

 seems to have at least as progressive teeth, but the canine is smaller. 

 The final test of relationship will depend on appearance of good skull 

 material for comparison. 



