PLATE 23 



SKULLS OF PROTOHIPPUS AND PLIOHIPPUS FROM THE UPPER MIOCENE OF TEXAS. 



All figures one-half natural size. 



Llano Estacado, Texas Lower Pliocene 1, la. Pliohippus fossulatus Cope, type, Univ. of Texas Coll. (cast Am. 



Mus. 14395). Lachrymal and malar fossa? moderately deep, 

 anterior in position, excavation continuing forward below nasals and 

 premaxillse. 1 Side view, la superior view of same skull, showing 

 undercutting below nasals and premaxillse. 

 " " " " " 2. Protohippvs pachyops Cope, type, Univ. of Texas Coll. (cast Am. Mus. 



14394). Lachrymal fossa anterior in position, restricted, rather 

 deep; no malar fossa. The generic and specific reference of this 

 immature skull and jaws is somewhat doubtful. 



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