PLATE 28 



UPPER TEETH OF PLIOHIPPUS FROM NEBRASKA, OREGON, AND TEXAS. 

 CHARACTERISTICS OF THE GENUS AND COMPARISON OF SPECIES FROM THE UPPER MIOCENE AND THE PLIOCENE. 



All figures natural size. 



Note the large cement lakes with relatively simple enamel borders, early and complete union of protocone to proto- 

 loph, and the tendency to later union with the metaloph. Characters are exaggerated in Pliocene species and lead into 

 Hippidium of the South American Pleistocene. 



Niobrara River, Nebr. Lower Pliocene 1. 



Rattlesnake, Ore. ?Pliocene 2. 



Snake Creek, Nebr. Lower Pliocene 3. 



Teleoceras quarry, Republican River, " 4. 



Long Island, Nebr. 



Llano Estacado, Texas Middle " 5. 



Pliohippus pernix Marsh, type, Yale Mus. 13007. 



P. spcctans Cope, type, Am. Mus. 8183. 



P. leidyanus Osborn, referred specimen, Am. Mus. 14004. 



P. nobilis Osborn, type, Am. Mus. 2668. 



P. simplicidens Cope, referred specimen, Am. Mus. 10624. 



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