326 University of California Publications in Geology [Vol. 12 



plication in the posterior wall. The outer face of the protoconid is 

 deeply rounded, that of the hypoeonid very slightly flattened. The 

 entoconid is large and full in the premolars, considerably reduced and 

 more oval in the molars. 



A reduction of the first in respect to the second molar is noted 

 in both the lower and upper cheek-teeth. The first molar, in the type 

 specimen held in a fragment of the jaw with P*, in anteroposterior 

 diameter is the least of the series. of the type specimen has been 

 somewhat cramped and deflected from the normal tooth line, to which 

 it lies superior. In the reduction of M- instead of IVP the form par- 

 allels the smaller Pliohippus forms of the underlying Eden beds (see 

 complete series under Eden). The lower series is referred to the form 

 represented by the upper teeth of the type specimen, being quite too 

 heavy for the smaller horse from the same formation. The more than 

 usual difference between the anteroposterior length of the third pre- 

 molar to second molar portion of the row in the upper and in the 

 lower series, i.e., 136 mm., versus 127 mm. (the sums of the separate 

 anteroposterior diameters) may represent individual variation and 

 difference in stage of wear. 



Measurements of Dentition of Pliohippus francescana, n. sp. 

 Type, Univ. Calif. Coll. Vert. Pal. 23277 



P-, anteroposterior diameter 35 mm. 



P^, transverse diameter 28.4 



P-, length of protoeone 12.5 



P-, anteroposterior diameter 35.6 



P-, transverse diameter 35.4 



P-, length of protoeone 9' 



pi, anteroposterior diameter 36.5 



P-, transverse diameter 34.8 



P-, length of protoeone 10 



Ml, anteroposterior diameter (34) 



Ml, transverse diameter 30 



Ml, length of protoeone 11 



M=, anteroposterior diameter 32.4 



M.-, transverse diameter 31.3 



M-, length of protoeone 13 



Eeperred Specimen, Univ. Calif. Coll. Vert. Pal. 23276 



Pr,, anteroposterior diameter 38 



Pi transverse diameter 18 



P3, anterojiosterior diameter 33 



P3, transverse diameter 19 



Pj, length of metaconid-metastylid column 19.5 



