PROMERYCOCHCERUS 



117 



Discussion: There are many dissimilar characters between this species and P. chelydra. On 

 the other hand, similarities certainly point to close relationship. This may be the male of Cope's 

 species, but it should be considered at least as a variety form until skeletal material of both species 

 is found. 



Promerycochoerus curvidens (Thorpe) 1921 

 Figs. 77-78 



Original Reference: John Day Promerycochoeri, with descriptions of five new species and one new 

 subgenus. Amer. Jour. Sci. (5), I, pp. 241-243, figs. 6 A, B (Desmatochcerus curvidens). 



Type Locality: North Fork, John Day River, 15 miles above junction with main stream, Oregon. 



Geologic Horizon: Upper Oligocene (middle John Day). 



Type: Holotype, Cat. No. 10997 Y.P.M., major portions of skull and mandible. Collected by L. S. Davis 

 in 1875. 



Specific Characters: The skull is small, not much larger than the larger species of Eporeo- 

 don. The maximum zygomatic expansion lies immediately in advance of the glenoid surface. The 

 malar is medium in depth below the orbit, and the anterior zygomatic pedicle continues forward 

 and upward as far as the infraorbital foramen as a strong convexity on the side of the face, more like 



Fig. 77. — Promerycoc/ixrus curvidens (Thorpe). 



Skull and jaw. HT. 

 Thorpe, 1921.) 



Cat. No. 10997 Y.P.M. 3/8 nat. size. (After 



Eporeodon than like Promerycochoerus . The squamous part of the arch is narrowest just in advance 

 of the glenoid surface and then rises moderately steeply to a low crest, bent inwardly, directly above 

 the glenoid surface, and about on a plane with the superior fourth of the orbit. The moderately 

 wide and unreduced nasal bones are posteriorly pointed, anteroposteriorly flat, and but slightly 

 convex transversely. The lacrimal fossa: are deep but small. The frontals are wide, flat, and unre- 

 duced, and are decurved above the orbits. The latter are medium-sized and subcircular, and have 

 the slightly longer axis horizontal. The temporal ridges unite above the glenoid surfaces. The low 

 sagittal crest is very short, less than a fifth of the skull length. The supraoccipital crest is mostly 

 missing but does not appear to have been greatly produced, and the wings are certainly close 

 together. 



The brain case is medium-sized, and the lateral ridge is anteriorly prominent. The external 

 auditory meatus is relatively large and directed almost entirely outward. The palate is narrow and 



