708 THE BRIDGER FAUNA. 



the nasal and attached part of the right maxillary bones. The portions 

 belong to a species of about the size of the Palceosyops horealis, and smaller 

 tlian any of the other species of the two genera here described. 



The nasal bones in profile have a horizontal superior surface. They 

 are very convex in transverse section, and their extremities are emarginate. 

 The infraorbital part of the malar is regularly convex, and overhangs the 

 maxillary bone extensively. Its postorbital limit is marked by an angle 

 directed at 45° inwards. The z3'gomatic part of the malar is flat externally. 

 The squamosar portion of the zygoma is not much elevated. The temporal 

 fossa is rather wide posteriorly, and the inferior temporal ridge is extended 

 horizontally. The postglenoid process is rather narrow and elongate. The 

 posttympanic process is robust, and is well separated from the postglenoid, 

 leaving an especially wide meattis auditorius. The front is flat, and the supe- 

 rior temporal ridges converge gradually to an isthmus, but scarcely form a 

 sagittal crest. The isthmus expands to the nan-ow lateral occipital crests. 



The occipital bone sends a long process forwards on the median line,- 

 forming a half-gomphosial articulation with the parietals. The lateral 

 suture of the two bones is considerably in advance of the posterior lateral 

 crest. The maxillomalar suture is on the convex infraorbital ridge. There 

 is a postparietal foramen; also a small one in the sqiiamosal bone posterior 

 to the position of the supraglenoid. There is above this a postsquamosal 

 on the parietal suture. 



The second true molar is abruptly larger than the first. In none of 

 the true molars are there ridges extending outwards from either of the- 

 internal cusjds, nor is there any posterior median tubercle. The anterior 

 median tubercle is distinct. Thei'C are no external nor internal basal 

 cingula, but the anterior and posterior are distinct. The latter, however, 

 only connects the two cusps of the posterior side of the crown. The outer 

 sides of the Vs have a trace of a median rib. The enamel is nearl}^ 

 smooth when worn, but finely rugose before protrusion. 



M. 



Length of true molar series ("2.75 inches) 0.067 



Leugth of last mol.^r 025 



Width of last molar 0J6 



Length of penultimate molar 0-26 



Wi«ith of penultimate molar 026 



Depth squamosal process 025- 



