with Descriptions of New Genera and Species. 101 



above incisor border. The right P^ has two accessory 

 pillars on the external face of the cone ; the left is normal. 

 It is possible that this may represent a new subspecies, 

 but in view of the fact that the specimen has suffered 

 marked lateral compression, it seems best for the present 

 to leave it under E. pacificus. 



Eporeodon trigonocephalus (Cope) 1884. 



Holotype, No. 7505, Cope Coll., A. M. N. H. Upper Oligocene (upper 

 John Day), North Fork, of John Day River, Oregon. 



Specific characters, — Palatonarial border produced 

 posterior to maxillary bones ; posterior nares shaped 

 like a shallow V ; small infra-orbital foramen above front 

 of P^ ; muzzle short ; paroccipital process not separated 

 from bulla by a groove ; high, thin sagittal crest ; bullae 

 small and ovoidal, with external ridge enclosing a groove 

 continuous with stylohyoid fossa, the long diameter 

 directed forward and inward ; lacrymal fossa well marked, 

 but shallow and confined to lacrymal bone ; nasal bones 

 blunt posteriorly ; skull flat and broad. 



The holotype is an old individual and nearly all of the 

 teeth are broken away. The matrix is light grey. In the 

 Marsh Collection, this species is represented by a 

 comparatively small number of skulls, all from either 

 Turtle Cove or Bridge Creek. These specimens, however, 

 differ from the type to a certain degree, but not enough to 

 invalidate the identification. 



Measurements of Holotype. 



mm. 



Total length of skull 201 



Bizygomatic diameter 145.6 



Superior molar series, length 36* 



Superior premolar series, length 41* 



Diameter, postorbital constriction 31.5 



* Approximate. 



Eporeodon trigonocephalus parvus, subsp. nov. 



(Figs. 4, 5.) 



Holotype, Cat. No. 12425, Y. P. M. Upper Oligocene (middle John Day) , 

 Haystack Valley, John Day Elver, Oregon. Collected by L. S. Davis in 1875. 



Specific characters. — In comparison with E. trigono- 

 cephalus, this subspecies shows the following differences : 



