BY CHARLES W. DE VIS, B.A. 223 



the concavity gradually decreases towards the outer edge, but on 

 the posterior surface of the outer edge itself is a strong fold (formed 

 of a revolution of the edge backwards) running upwards from the 

 base and subsiding as it reaches the cutting edge. The outer or 

 fore surface of the tooth is curved longitudinally and transversely, 

 and is covered with shallow confluent excavations. The diastema 

 is long, being nearly equal in length to the space occupied by the 

 three anterior grinders. It descends from the premolar with a 

 gentle curve, and rises with a slighter curve to the incisive outlet. 

 Commencing about four lines in front of the vertical from the 

 premolar, the symphysis presents a long moderately deep and 

 nearly horizontal syndesmotic surface, with longitudinal rugse. 

 The union of the mandibles through much broader and 

 firmer than in Macropus, is far inferior in those respects 

 to that of Procoptodon, and corresponds rather with that of 

 Sthenurus. The same observation applies to the direction in 

 which the incisor is implanted. The dental foramen is midway 

 between the vertical from the premolar and the incisive outlet, 

 and is six and a-half times below the mediasternal ridge, in both 

 respects differing much from its position in Macropus. A 

 longitudinal groove commences at the vertical from the fore 

 lobe of d 4 and gradually deepening as it runs backwards, 

 separates the lower border of the mandible from the sub-alveolar 

 convexity, which increases rapidly below the permanent molars. 

 The groove ends rather abruptly at the origin of the inflected angle. 

 The postal veolar angle is prominent, the outer alveolar groove, 

 narrow and shelving. On the outer side anteriorly, the alveolar 

 ridge is well separated by compressure from the subalveolar 

 convexity beneath the premolar, and is continued backwards from 

 the diastema in a straight slope to the middle of m 1 . The sub- 

 alveolar convexity subsides considerably beneath d 4 , but again 

 increasing, is at its greatest at the base of the coronoicl process. 

 This process appears to rise at a comparatively low angle. On 

 the same parallel with the base of the coronoid process, is the 

 commencement of the ridge bounding the outer crotaphyte fossa 

 posteriorly — but the lower brim of that fossa does not present 

 itself between the two points as it does in Macropus. 



