PLATE 26 



PREORBITAL FOSSAE IN MERYCHIPPUS AND PLIOHIPPUS. 



COMPARISON OF MERYCHIPPUS CAMPESTRIS, MIDDLE MIOCENE, AND THREE SPECIES OF PLIOHIPPUS FROM THE UPPER 



MIOCENE AND LOWER PLIOCENE. 



All figures one-half natural size. 



Pawnee Creek, Col. Middle Miocene 1. Merychippus campcstris Gidley, referred specimen, Am. Mus. 9459. 



Lachrymal and malar fossae deep, well separated. 

 Little White River, So. Dak. Lower Pliocene 2. Pliohippus supremus Leidy, referred specimen, Am. Mus. 10844. 

 " " " " " " " 3. Pliohippus mirabilis Leidy, type, U. S. Nat. Mus. 569 (drawn 



from cast Am. Mus. 10840). 



Republican River (Telcoccras 4. Pliohippus nobilis Osborn, type, Am. Mus. 2668. Malar fossa 



quarry), Long Island, Nebr. distinct, deep; lachrymal fossa distinct anteriorly. 



274 



