EPOREODON g3 



Mandible: The symphysiodental angle is 50°, and the chin is straight in profile. The hori- 

 zontal ramus gradually increases posteriorly in depth. The mental tubercle is small. The coronoid 

 process is thin and much higher than the condyle. The latter is transversely wide and strongly 

 convex anteroposteriorly. The sigmoid notch is small. 



Foramina: The infraorbitals are above the middle of P 3 . The supraorbitals are 10 mm. apart. 

 The posterior palatine foramina are opposite P\ 



Dentition: The superior molar-premolar index is 0.918, and that of the lower series is 0.86. 



Skeleton: As stated by Marsh (1873, p. 410): 



The metacarpals are slender .... The first is wanting. The third and fourth are nearly equal in size, and 

 had their coadapted faces immovably united by cartilage. The second and fifth are both well developed. The 

 navicular and cuboid bones were loosely coossified, or separate. The phalanges are much more slender than in 

 the Peccaries. 



Discussion: A skull, Cat. No. 12316 Y.P.M., possesses natural casts of the bullae which are 

 divided into anterior and posterior hemispheres. Of the specimens of this species in the Marsh Col- 

 lection 23.8 per cent died in the milk dentition stage, and no individuals reached an old age. 



Eporeodon pacificus (Cope) 1884 

 PI. VIII, figs. 1-3 



Original Reference: Synopsis of the species of Oreodontidte. Proc. Amer. Philos. Soc, XXI, pp. 518, 

 519 (Eucrotaphus jacksoni facificus). 



Synonym: Eporeodon occ'identalh pacificus Merriam and Sinclair 1907. 



Type Locality: John Day River, Oregon. Referred specimens from Turtle Cove, Haystack Valley, 

 Bridge Creek, Clarno Bottom, and five to six miles below Cottonwood, John Day Valley, and from the North 

 Fork of the John Day River, as well as from Crooked River, Oregon, and from White Buttes, South Dakota. 



Geologic Horizon: Upper Oligocene (middle John Day), for the most part, but also probably lower 

 Miocene (upper John Day). 



Type: Holotype, Cat. No. 7502 A.M.N.H., an excellently preserved skull, collected by C. H. Sternberg 

 and J. L. Wortman. 



Specific Characters: The skull is long and mesocephalic and about the size of that of 

 E. major. The zygomata reach their maximum expansion at about the middle of the zygomatic 

 foramina. The malar part is deeper and more robust than the squamosal portion of the arch, which 

 rises very gently aft. The nasals are very long, extending aft to a point through the anterior third 

 of the orbits. They are posteriorly pointed and elliptical in shape. The lacrimal bone has a large 

 pars facialis quadrilateral in shape, with a large, deep fossa therein. The frontals are large, slightly 

 depressed medially, and moderately convex laterally. They extend in advance of the lacrimal bones. 

 The orbits are moderately large and look almost wholly sidewise. The temporal ridges unite above 

 the anterior third of the glenoid surfaces to form a thin sagittal crest, somewhat less than a third of 

 the skull length. The supraoccipital crest is well produced beyond the occipital condyles, and the 

 wings are close together. The brain case is rather small, with a well-marked ridge along the parieto- 

 squamosal suture. The external auditory meatus is large and tubular and directed very markedly 

 backward but only slightly upward. The palate is wide and somewhat vaulted, and the U-shaped 

 palatonarial border is nearly on a line with the posterior of the maxillary bones. The basicranial 

 axis is shallow. The glenoid surface is anteroposteriorly wide and nearly flat, while the postglenoid 

 process is stout but rather small and not in contact with the bulla. The bulla? are large and laterally 

 compressed and have a small anterior prolongation, not otherwise seen in Eporeodon but similar to 

 the condition which occurs in Leptauchenia and Cydopidius. The paroccipital process is slender, 

 and the greater diameter is transverse. Index: 0.56. 



Foramina: The infraorbital lies above the posterior of P 3 . The supraorbitals are very close to 

 the sagittal suture, being but 1 1 mm. apart, and the shallow grooves, which lead forward, are 

 nearly confluent. 



Dentition: The superior molar-premolar index is 0.85. P 4 is proportionally large. 



