PROTHEOSODON CONTIFERUS 43 
“pillar”? already developed opposite the posterior end of 
the back crescent. In fact, the tooth is molariform, except 
as to the tiny extra cusp found on the molars. Premolar 
4 is more completely molariform consisting of the same 
parts as the preceding tooth. 
The molars may be distinguished by the presence of a 
tiny median cusp on the rear of the tooth, behind the cres- 
cent, which, when the tooth is worn, makes a median spur 
to the rear. In both the premolars and molars, the teeth 
are characterized by their plumpness, and the isolation 
and lowness of the cusps. 
ates i Reno Stee sheer 
ES Some 
Fig. 16. Right mandible—1/2 natural size. 
The two halves of the lower jaw are completely fused at 
the symphysis. The horizontal ramus is thick, but low 
dorso-ventrally, giving the appearance of a slender jaw. 
The posterior angle is prolonged backward and bent in- 
ward. The fossa for the masseter muscle, while large, is 
but faintly outlined. The ascending ramus hardly rises 
above the level of the teeth, except as the slender coronoid 
projects to a good height above the articular condyle 
and curves backward over it. 
