ivith Descriptions of New Species. 22 T 



and delimited between anterior and posterior borders of 

 postgienoid process ; lacrymal fossa small but well devel- 

 oped; orbits very liigli; skull longer than P. superbus] 

 very strong convexity above foramen magnum. 



This species is not so robust as either P. chelydra or 

 P. latidens. The face is strongly convex above the infra- 

 orbital foramen, due to an upward-sloping ridge from the 

 anterior zygomatic pedicle to the nasals. The orbits are 

 directed but very slightly upward. The orbit is deeper 

 than wide. The posterior part of the zygoma rises to the 

 plane of the summit of the sagittal crest, which is not 

 true of any other species. Its apex is above the external 

 base of the postgienoid process. The prominence of the 

 ridge along the parieto-squamosal suture is very variable, 

 although it is a constant feature in all genera of the 

 Oreodontid{:B (Merycoidodontidas). The marked convex- 

 ity above the foramen magnum is separated from the 

 posterior temporal angles by well defined lateral fossae, 

 which, however, are much smaller and less deep than in 

 P. latidens. The mastoid and paroccipital processes do 

 not close the auricular fossa below, but do approach close 

 to the postgienoid tubercle, which is wide and robust and 

 its height and thickness are equal. The bullae are the 

 smallest known in the genus. The palate is concave 

 between the first true molars, while it is flat between the 

 premolars. The infra-orbital foramen is large. The 

 incisive foramina are large and oval-shaped, whereas in 

 P. chelydra they are triangular. 



The inferior edge of the ramus is straight below the 

 tooth-row, except for the symphysial tuberosity, which, 

 instead of being an individual peculiarity as Cope sug- 

 gested, is found in all of the species of this genus. It is, 

 however, subject to much variation in its development. 

 The coronoid process is small and everted. The anterior 

 inner edge encloses an elongate, well defined fossa. The 

 masseteric fossa in the type is fairly shallow, although 

 this appears to be a variable character. The premolars 

 are large and the first three are two-rooted, while P^ is 

 separated by a marked diastema on either side, the 

 greater being between it and the canine. The molars 

 lack the internal cingTila. Po is rudiment al in that it has 

 a prominent internal vertical ridge. The true canine is 

 very wide. The incisive alveolar border overhangs a 

 symphysial concavity. The lower incisors are crowded 

 and overlap each other and the true canine. 



