580 Bulletin American Museiwi of Natural History. [Vol. XIX, 



notch separating the coronoid from the condyle, and passes 

 backward and upward in a sharp ridge, forming the outer 

 articular border of the condyle. The articular surface is 

 slightly rounded. 



The dental canal begins in a deep elliptical depression at a 

 point below the origin of the condyle and passes forward to 

 the entry of the large dental foramen. It continues forward 

 in two divisions: the smaller and shorter, opening on the 

 outer side of the jaw, opposite the posterior border of the 

 last molar; the larger, passing forward and dividing into three 

 branch canals that open on the outer side of the jaw where it 

 bends forward to form the symphysis. These foramina are 

 about 10 mm. apart, and the middle one is the largest. The 

 smaller ones are about one fourth the diameter of the larger 

 one. Near the depression that gives rise to the dental canal 

 is a narrow deep channel that passes downward and forward 

 under the upper part of the ridge bounding the concavity of 

 the angle where it divides and comes to the surface in two 

 foramina 20 mm. apart. 



Tibia. 



The tibia is a short, massive bone with a flattened shaft. 

 The proximal end is greatly expanded laterally and in width is 

 about three fourths of the entire length of the tibia. In 

 general appearance and proportions it agrees with the type 

 of M. robustus with the following exceptions. The external 

 condylar facet is distinctly pyriform. In M. robustus it is 

 circular. The fibular facet is elliptical and slightly concave; 

 oblique to the condylar surface and sloping from without in- 

 ward and downward. Anteriorly it nearly meets the superior 

 surface. Posteriorly they are separated by a convex facet 

 for the articulation of a sesamoid. The distal articular sur- 

 face is divided as in M. robustus, but the external semi-elliptical 

 compartment is convex, while in M. robustus it is fiat. The 

 external malleolus is not as prominent as in M. robustus. 



Fibula. 

 The fibula is a subprismatic bone enlarged at both ends. 

 The outer surface of the shaft is convex; the inner surface 



