988 THE JOHN DAY FAUNA. 



of the infraorbital foramen the face is gently and regularly convex to the 

 premaxillary border. The premaxillary ascending ramus is long, but does 

 not appear to reach the froutomaxillary suture. The fragment of the front 

 shows that the temporal ridges converge gradually, and that the middle line 

 is concave. The posterior part of the skull shows a high sagittal crest and 

 inion, and a brain case of the absolute size of that of the P. platycopis, and 

 therefore relatively larger. The inferior part of the lateral occipital crest 

 is obsolete, continuing into a low rounded ridge which is continued as the 

 prominent superior border of the meatus auditorius externus. A posterior 

 ridge goes to the external superior base of the paroccipital process; another 

 ridge extends from the internal superior base, and the space between 

 is divided by a median ridge. The paroccipital itself is short and is directed 

 backwards. A perpendicular ridge descends from its external base to the 

 posterior angle of the posttympanic process. The latter has a truncate 

 downlooking extremity of a triangular form; the longest side being ante- 

 rior, and the internal and external angles of about equal length. The 

 occipital condyles are rather small. 



Foramina. — The / infraorhitale is large. So is the / postparietale, which 

 is situated immediately at the base of the sagittal crest, or higher up than 

 in any of the species here described. The mcahis auditorius externus is con- 

 tracted, owing to the more than usual appi-oximatiou of the posttympanic and 

 postglenoid processes. 



Dentition. — The bases of the crowns of the superior incisors are so robugt 

 and the external so cylindric, as to render it very probable that their form 

 is conic, as in the P. plati/copis The superior canine is large, and has a lentic- 

 ular section at the base of nearly equal acumination of front and rear. The 

 posterior edge is denticulate. (See specimen No. 2.) The second (first) 

 premolar is quite small, and is situated two-thirds way from the canine to 

 the third premolar. Its root is grooved on the inner side, but I cannot say 

 whether it is double. The third premolar is large, and is separated from the 

 canine by a space five-sixths the diameter of the latter. There are no other 



teeth in the specimen. 



Measurements of Ro. 1. m. 



Elevation from diastema to frontomaslUary suture 0G9 



Width from orbit to premaxillary nareal border 036 



Length of bases of three incisors 010 



