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University of California Publications. [Geology 



corresponding tooth of P. borealis (Cope) and resembles it in 

 some other respects. As in P. borealis, the adjacent horns of the 

 inner crescents are completely fused at their tips, and there is a 

 well defined spur, or crotchet, extending forward into the an- 

 terior fpssette. The anteroposterior diameter of the tooth is 19.5 

 mm., transverse (estimated) 22 mm. 



The other tooth referred to this genus is a considerably worn 

 premolar of the left side (no. 10671). It shows nothing of 

 special importance. 



CONCLUSIONS. 



Without exception the specimens of this little collection indi- 

 cate species of a middle or lower Miocene age. Compared with 

 the known forms of the Mascall beds of the John Day Valley, the 

 species appear to differ slightly in every case, and the species of 

 Merychippus represented are apparently somewhat more primi- 

 tive throughout. This leads to the conclusion that the Virgin 

 V alley beds are not newer, at least, and suggests that they may be, 

 in fact, somewhat older than the Mascall formation. 



Date of Issue, December 2, 1908. 



