268 G. T. BETTANY ON THE GENUS MEKYCOCBXEKUS. 



glenoid surface. Its breadth is about equal to the distance between 

 the middle line and the outer edge of the glenoid surface. Between 

 the postglenoid tubercle and the outer margin of the zygoma the 

 latter forms a wide concavity ; for the lower edge of the zygoma at 

 its most j>rominent part descends to as low a level as the apex of the 

 auditory bulla. The surface is smooth. The lower fork of the 

 malar extends backwards, beneath and internally to the zygoma, 

 lying on it, but not anchylosed with it, as far as the region of the 

 great transverse crest. It ends in a thin flat rounded lamina. The 

 posterior surface of the crest is smooth and slightly concave below. 



The palate is broad and arched, and only widens slightly between 

 the molar teeth. There is an anterior major concavity between the 

 premolars and the first two molars of each side, and a posterior 

 smaller concavity behind the level of the last molars. The palate 

 is continued behind the alveolar processes for about one third of the 

 distance between them and the auditory bullae ; its width di- 

 minishes to about half that of the anterior portion; and there is a 

 deep notch on each side between this posterior portion of the palate 

 and the alveolar processes. The palatal surface ends by a posterior 

 edge which possesses a median prominence and two lateral shallow 

 concavities, which pass on each side into the vertical pterygoid plates. 

 The latter extend, at about the same level as the palate, nearly back 

 to the auditory bullae, and consequently enclose a large and deep 

 median fossa behind the palate. I am not able to describe the ptery- 

 goid fossae ; they were certainly comparatively small. 



The teeth do not need much remark, since Leidy has described 

 the teeth of Oreodon so elaborately in the * Extinct Mammalian 

 Fauna of Dakota and Nebraska,' and those of Merycochoerus do 

 not differ from them in many points except those mentioned in the 

 generic definition given above. One of the most conspicuous cha- 

 racters appears to be the more rapid increase of the molars in size 

 from before backwards, and the increased strength of the external 

 columns of the upper molars. 



The lower jaw exhibits a considerably, greater size and prominence 

 of the lower posterior rounded angle than in Oreodon. The con- 

 dyles are very narrow, and are transversely elongated. The as- 

 cending rami are vertical, and consequently parallel to one another. 

 Their external surfaces are concave posteriorly and convex ante- 

 riorly, the convexity being lost on the horizontal rami. The as- 

 cending rami are most remarkable for their breadth, though their 

 height is considerable. The horizontal rami are not very deep ; 

 they are vertical, but have a strong convexity externally, proceeding 

 from behind and above obliquely downwards and forwards to the 

 lower extremity of the ramus. The mental foramen is large, oval, 

 and directed obliquely forwards ; it is placed just below the third 

 premolar (the caniniform tooth being reckoned as the first). The 

 anterior symphysial surface of the jaw is broad, in correspondence 

 with the breadth of the row of incisor teeth with the caniniform 

 premolar. It is twice as broad above as below, and is regularly 

 convex from side to side. From its lower extremity it ascends at 



