with Descriptions of Neiv Species. 243 



anterior part of the zygoma is neither wide nor robust, 

 but has much the shape found in Eporeodon; (6) from the 

 matrix and other factors it is very probably a middle 

 John Day form, this horizon having produced the greatest 

 number and variety of species of Eporeodon. 



Measurements of Holotype. mm. 



Length of skull, condyles to prosthion inc 279 



Bipostglenoid diameter 95 



Bizygomatic diameter 153 



Length of superior molar series 68 



Length of superior premolar series 55 



Length of superior dental series, inc. canine 146 



Max. width of cranium 70 



Max. height of zygoma above glenoid surface 46 



Width of f rontals above middle of orbits 76 



Length of inferior molar series 73 



Length of inferior premolar series 62 



Depth of ramus below M^ 38 



Synopsis of Chaeactees of John Day Species of 

 Peomeeycochceeus. 



1. Infra-orbital foramen above middle of P^ ; palate 

 moderately produced posteriorly. 



Orbits small, nearly round; internal cingulum on 

 superior molars; skull elongated; bullae large: 

 lacrymal fossa very shallow; incisive foramina 

 right-triangular, with longest leg along sagittal 

 plane P. superhus. 



No internal cingulum on superior molars; greatest 

 bizygomatic diameter anterior to glenoid process ; 

 bullae small, subcorneal; incisive foramina wider 

 than long and close to base of canines .P. chelydra. 



Orbits nearly circular ; internal cingulum on superior 

 molars ; lacrymal fossa conical, deep ; incisive 

 foramina nearly semicircular and close to incisor 

 margin; bullae large; smaller than P. superhus 

 P. leidyi. 



Orbits looking outward, not upward; lacrymal 

 fossa very deep, large; skull long, slender; sagit- 

 tal crest exceedingly high and thin; bullae large, 

 compressed ; occiput above foramen magnum very 

 narrow and convex P. lulli. 



Orbits looking chiefly outward ; lacrymal fossae well 



