PROMERYCOCHCERUS 



137 



Promerycochoerus microcephalus Thorpe 1921 

 Figs. 94-95 



Original Reference: John Day Promerycochceri. Amer. Jour. Sci. (5), I, pp. 239-240, figs. 5 A, B. 



Type Locality: Turtle Cove, John Day River, Oregon. 



Geologic Horizon: Upper Oligocene (middle John Day). 



Type: Holotype, Cat. No. 10998 Y.P.M., skull, somewhat laterally compressed but well preserved, except 

 for portion anterior to P 1 which is broken away. Left ramus without canine and incisor border; right also lack- 

 ing Pj and parts of M 2 and M 3 . Collected by William Day in 1875. 



Fig. 94. — Promerycochoerus fuicrocephalus Thorpe. Skull and jaw. HT. Cat. No. 10998 Y.P.M. 1/3 nat. size. 



(After Thorpe, 1921.) 



liiii»'T.a£i 



Fie. 95. — Promerycochoerus microcephalus Thorpe. Left half, superior view of skull. HT. Cat. No. 10998 Y.P.M. 



1/3 nat. size. (After Thorpe, 1921.) 



Specific Characters: The skull is about the length of that of P. chelydra but is only slightly 

 more than half as wide. It is one of the three dolichocephalic skulls in the genus. The maximum 

 zygomatic expansion is opposite the zygomatic foramen. The malar below the orbit is very deep 

 and heavy, with its inferior edge convex downward. The squamous portion of the arch invades the 

 malar to a point below the posterior third of the orbit, and is there sharply truncated. This process 

 does not descend but soon rises abruptly, and near the apex curls strongly backward, with its highest 

 point but slightly above the level of the squamous suture. The external edge is rounded but is 

 neither heavy nor rugose, and the squamous part is relatively light in comparison with the malar 



