FOSSIL HORSE REMAINS FROM IDAHO GAZIN 



297 



show one or two antero-external grooves (fig. 21, no. 12541). In 

 specimens where the styles are somewhat constricted inwardly the 

 flattened lateral surface of the style is faced sharply forward. The 

 concavity between the styles in many specimens is more acute in the 

 first two molars than in the premolars as in no. 12546 (fig. 21). 



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Figure 21.— Plesippus thoshonensis Qidley. Eoamel patterns of left upper cheek teeth in 

 seven selected individuals arranged according to age. In the first two dentitions the pre- 

 molars belong to the deciduous set. U.S.N.M. nos. (from top to bottom) 12494, 12520, 12541 

 12643, 12576, 12546, and 12548. One-half natural size. Hagerman lake beds, upper Pliocene'. 

 Idaho. 



48610—36 3 



