1884.1 OAd 



[Cope. 



The mandible possesses some distinctive characters. The angular 

 border is not prominent posteriorly, extends forwards below, and projects 

 below the general level of the inferior border of the ramus. Neither of 

 these characters is observable in the only ramus of the M. superbus in 

 which the lower part of this border is well preserved, but in some others 

 of that species the superior part of the border is much as in M. macro- 

 stegus. The inferior edge of the ramus is straight, but there is a descend- 

 ing tuberosity of the symphysis which may be an individual peculiarity. 

 The symphysis is very concave in profile, and the incisive border is pro- 

 duced in accordance with the prolonged muzzle. In the M. superbus it is 

 sometimes convex, sometimes a little concave, but not so much so as in 

 this jaw. The coronoid processes are small and slightly everted. The 

 inner ridge of its anterior base is more prominent than the exterior, and 

 encloses a fossa with it. The masseteric fossa is not noticeable. There 

 is one large mental foramen below the third premolar. The dental fora- 

 men is large and oval, and when the mandible stands on a level surface is 

 opposite the middle lobe of the third inferior molar tooth. 



In dentition this species is distinguished by the relatively large size of 

 the premolar teeth, of which the first, second and third are two-rooted in 

 both jaws. Both the first and second in the upper jaw have short diaste- 

 mata anterior and posterior to them, the largest being behind the canine 

 tooth, and nearly as long as the premolar's crown. All the teeth are a 

 good deal worn in the specimen. One can see two internal cingula in- 

 closing fossae on the third premolar. The true molars increase in size 

 rapidly posteriorly and the third has a well -developed external heel. The 

 molars have no internal cingula ; these are present in five of seven skulls 

 of the M. superbus where these parts are cleaned. The most noteworthy 

 point in the mandibular dentition is a very rudimental character of the in- 

 ternal vertical ridge of the crown of the first premolar. The posterior 

 fossa of the fourth premolar is closed, and the anterior remains open, on 

 wearing. In M. superbus both are closed in the specimen where visible. 

 The anterior inner wall is represented in the second and third premolars 

 by a cingulum. No cingula on the true molars. First premolar very ro- 

 bust, its section lenticular. 



. . Measurements. M. 



Axial length from occipital condyles* to premaxillary 

 border .345 



Axial length from occipital condyles to postglenoid pro- 

 cess 045 



Axial length from occipital condyles to postfrontal pro- 

 cess 138 



Axial length from occipital condyles to palatonareal 

 border , .100 



*The occipital condyles are broken off in the specimen, so I measure from the 

 superior border of the foramen magnum, whicb is, in the other species, in the 

 vertical line of the occipital condyles. 



