EOCENE AND OLIGOCENE TITANOTHERES OF MONGOLIA 



921 



As shown in our cranial sections of Dolichorhinus 

 Jiyognathus { = cornutus) of Wyoming and Utah, the 

 occiput is relatively small, low, flaring toward the top; 



processes; anteriorly there is a rounded rather than 

 angulate suborbital malar bar. The mandibular rami 

 are readily distinguished from those of Protitanotherium 



Figure 777. — Comparative views of the superior and inferior grinding teeth of Dolichorhinus kaiseni 

 and of the lower jaws of D. kaiseni and Protitanotherium grangeri 



A, External aspect of the grinding teeth of D. laiseni (Am. Mus. 20260), one-halt natural size; B, left lateral aspect of female jaw of 

 J), kaiseni (Am. Mus. 20255), one-fourth natural size; C, right lateral aspect of Protitanotherium grangeri jaw (Am. Mus. 20105), 

 one-sixth natural size. Observe the marked diflerenoe in the form of the coronoid, In the elevation of the condyle, and in the con- 

 tour of the angle in the lower border of the ramus, in the two species. 



the condyles are relatively small, sharply convex; the 

 zygomata are extremely slender, elongate, sharply 

 angulate as they turn inward toward the postglenoid 



by three characters — (1) the marked external muscular 

 sculpturing of the coronoid and condylar regions; (2) 

 the backward extension and downward curvature of 



