PHENACOCCELUS 



183 



moderately strong bar, are more elevated than in Merycoidodon, and look much more upward than 

 in that genus, being suggestive of Leptauchenia. The frontals are moderately flat, with a slight 

 elevation along the sagittal suture. They are narrow and extend forward in advance of the lacrimals. 

 The temporal ridges are no more prominent than in Merycoidodon and join close to the fronto- 

 parietal suture to form a moderately long, but rather low, sagittal crest. The supraoccipital crest 



Fie. 132. — Phenacocaelus tyfus Peterson. Skull. GUT. C.it. No. 1263 CM. 1/2 nat. size. (After Peterson, 1906.) 



overhangs the condyles by a considerable margin, and the wings are fairly widespread. There is a 

 large and deep excavation on either side of the occiput just below the junction of the sagittal with the 

 lambdoidal crest. 



The brain case is relatively larger than in Merycoidodon, with a prominent ridge along the 

 parietosquamosal suture. The external auditory meatus lies in the normal merycoidodont position, 

 directed outward and somewhat upward and backward. The palate is moderately narrow and 



Fig. 133. — Pheiucocazlus tyfus Peterson. Superior view of skull. PT. Cat. No. 1276 CM. 1/2 nat. size. 



(Drawn from Peterson, 1928.) 



slightly uparched, while the open V-shaped palatonarial border is on a line across the posterior 

 parts of the alveolar parapet. The glenoid articular surface is anteroposteriorly convex on two- 

 thirds of the outer surface ; farther back it is concave in the same direction. The postglenoid 

 process is relatively heavy. The paroccipital process is prominent, trihedral in section, and closely 

 appressed to the bulla. The bulla? are very large and somewhat similar in shape to those of 

 Leptauchenia and Cyclopidius. The basicranial axis forms an arch, curving gently forward. 

 Index: 0.54-0.58. 



Mandible: The symphysis is deep and strong, with the dentosymphysial angle approximately 

 40°. The symphysis is slightly concave vertically, with a small tubercle inferoposteriorly. The 



