568 



University of California Publications in Geology [Vol. ll 



Measurements op Upper Milk Molars 



No. 21199 



Dm 4 , anteroposterior diameter 26.5 mm. 



Dm 4 , height of slightly worn crown, measured on protoeone .... 14 



No. 19443 



Dm 3 "?, anteroposterior diameter 24.5 



Dm 3 ?, height of somewhat worn crown, measured on protoeone 9 



In a large lower milk molar (no. 21315, fig. 190), the crown is high 

 and narrow and shows a thick cement layer. The parastylid extends 

 inward beyond the metaconid. The metaconid-metastylid column is 

 narrow transversely in the section exposed, and the gutter is narrow. 

 This specimen probably represents the same species as the large lower 

 teeth no. 21346 referred to P. fairbanksi. 



Fig. 190. PlioMppus fairbanksi? Merriam. Dm,, no. 21315, natural size. 

 Ricardo Pliocene, Mohave Desert, California. 



Figs. 191 and 192. PlioMppus fairbanksi? Merriam. Superior milk molars, 

 natural size. Fig. 191, Dm 4 , no. 21199; fig. 192, no. 21210. Ricardo Pliocene, 

 Mohave Desert, California. 



Measurements of no. 21315 



Dm,, anteroposterior diameter 32 mm. 



Dm,, transverse diameter 12 



Dm 4 , height of crown 26.6 



EQUID SKELETAL ELEMENTS 



A number of limb bones from Ricardo represent horses consider- 

 ably larger and of more advanced type than those from the beds of 

 the Barstow syncline. The phalangeal elements and the metapodials 

 represent at least two horse types. In no. 21200 (fig. 195) the prox- 

 imal phalangeal element is larger and more slender than in any of 

 the Merychippus or Protohippus forms from the Barstow. It is 

 longer and much more slender than in Hypohippus. It is smaller 



