PLATE 11 



PREORBITAL FOSSJE IN MERYCHIPPUS. 

 COMPARISON OF SKULLS IN FOUR SPECIES. 



All figures one-half natural size. 



Pawnee Creek, Northeastern Colorado Middle Miocene 1. Merychippus sejunctus Cope, type, Am. Mus. 8291. 



Lachrymal and malar fossa? shallow, obscurely separated. 

 " ." " " " " 2. M. paniensis Cope, referred specimen, Am. Mus. 9382. 



Lachrymal fossa deep, extensive; malar fossa not differ- 

 entiated. 



" " " " " " 3. M. proparvulus Osborn, type, Am. Mus. 9394. No malar 



fossa. 



Snake Creek, Sioux County, Nebr. ?Lower Pliocene 4. M. calamarius Cope, referred specimen, Am. Mus. 14001-2. 



Lachrymal and malar fossse distinct, well differentiated. 



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