EPOREODON 71 



well in advance of the lacrimals. The orbits are rather small and look almost wholly sidewise. 

 The temporal ridges join at the front of the glenoid surfaces to form a long, high, and thin sagittal 

 crest, in length somewhat less than a fourth of the length of the skull. The profile of the sagittal 

 crest is moderately concave, rising posteriorly to join the supraoccipital crest, which is well produced 

 aft, with the wings widespread. The brain case is long and narrow, with a prominent convexity 

 along the parietosquamosal suture. The external auditory meatus is medium in size, with a direc- 

 tion slightly backward as well as upward and outward. The basicranial axis is shallow. The 

 V-shaped palatonarial border is nearly on a line with the last molars, while the palate is narrow 

 and gently vaulted. The skull, especially in the palate, has suffered some lateral compression. The 

 glenoid articular surface is moderately small and slightly convex, while the postglenoid process is 

 stocky, with a transverse diameter somewhat greater than the anteroposterior which is in contact 

 with the bulla. The bulla is large and laterally compressed. The paroccipital process has the long 

 diameter extending forward and outward at the base but soon becomes strongly compressed down- 

 ward. Index: 0.45. 



Mandible: The ramus is shallow below the tooth row. The masseteric fossa is shallow and 

 much more vertical than that of E. Occident alts. 



Foramina: The infraorbitals lie above the middle of P 3 . 



Dentition: The molar-premolar index is 0.88. 



Discussion: A skull, Cat. No. 10145 Y.P.M., is regarded as that of a male because of the 

 longer dental series, much heavier and more robust canines, wider palate and frontal bones, larger 

 brain case, square muzzle, and in general the more pronounced robustness of skull in comparison with 

 some of the other skulls of the same species in the Marsh Collection. The paramastoid processes 

 are very heavy, but the postglenoid tubercles are abnormally small, and P 1 and P 2 are obliquely 

 placed. This specimen was collected by William Day at Turtle Cove in 1875. 



Another skull, Cat. No. 12408 Y.P.M., from the North Fork of the John Day River, is 

 referred to this species but shows certain divergent characters. For example, the molar and pre- 

 molar series are nearly equal in length, and their combined total is 91 mm., the same as that of 

 E. pacificus, but the skull length is normal for E. leptacanthus. The origin of the zygoma is 

 heavier, and the face is more prominently divided by the forward prolongation of that process. The 

 nasals are wedge-shaped, becoming progressively wider as they advance. The lacrimal fossae are 

 shallower. The postglenoid process is smaller, the paroccipital process turns obliquely outward, and 

 the sagittal crest is shorter. Three skulls, Cat. Nos. 12409, 12410, and 12414 Y.P.M., all exhibit 

 the same characters as does Cat. No. 12408. 



The specimens of E. leptacanthus in the Marsh Collection indicate that, of the material in this 

 museum, 6.1 per cent died while having the deciduous dentition and only 1.5 per cent reached old 

 age; the majority died in their prime. 



Eporeodon longifrons (Cope) 1884 

 PI. V, figs. 1-3 



Original Reference: Synopsis of the species of Oreodontidas. Proc. Amer. Philos. Soc, XXI, p. 520 

 (Eucrotaphus major longifrons). 



Synonym: Eporeodon major longifrons Merriam and Sinclair 1907. 



Type Locality: North Fork of John Day River, Oregon, according to Cope's statement. Data in the 

 American Museum, however, indicate that the type was collected at "the Cove," which is not on the North Fork 

 but several miles up the lohn Day River above the mouth of the North Fork. Referred specimens were collected 

 at Haystack Valley, at Turtle Cove, and five to six miles below Cottonwood Creek. 



Geologic Horizon: Lower Miocene (upper John Day). 



Types: Holotype, Cat. No. 7504 A.M.N.H., skull, collected by C. H. Sternberg. Plesiotype, Cat. No. 

 11020 Y.P.M., skull and jaws attached by matrix. The lower jaw measurements are taken from this specimen, 

 although it is somewhat larger than the type skull. 



