384 E. L. Troxell — Entelodonts in Marsh Collection. 



very heavy. It is much larger than M 1 ; has the cusps 

 grouped closely together and the cingula distinct, but 

 weak on the corners. M 3 is round except for the prom- 

 inent base of the paracone. The metacone is very much 

 undeveloped, likewise the hypocone ; the hypo style is not 

 as prominent as in A. clavus clavus, and there is no pos- 

 terior heel. 



Along with the great development of the zygomatic 

 arch and its dependent process, we find greatly enlarged 

 tubercles on the lower jaws (see fig. 12). The anterior 

 mental processes are about half below the large canines, 

 and are well in front of the beginning of the symphysis. 

 They are rounded, flat on the bottom, and larger at the 

 ends, which hook backward. The chin is flat in front of 

 the tubercles and only slightly convex near the incisive 

 border. The symphysis is short and the body of the 

 ramus relatively light in this specimen. 



The processes below the fourth premolars do not ex- 

 tend so far laterally from the rami, but they are com- 

 pressed and spread anteriorly to join small secondary 

 tubercles. The posterior outer corner is rounded up and 

 backward. 



The coronoid process rises well outside the line of the 

 molars as in specimen No. 10032. It is round, thick, and 

 heavy, although the antero-posterior dimension is not 

 great and the masseteric fossa encroaches from below, 

 causing the branch down and forward, and that running 

 back, to be narrow and rounded. The masseteric fossa is 

 large and deep like that of a carnivore and is roughly 

 pentagonal in form. The border below forms a strong 

 buttress running to the tip of the condyle. 



The mental foramen lies above the mental tubercle and 

 below Pi. Apparently other smaller foramina lie further 

 back. 



There exists a considerable difference in size between 

 the alveoli of \ x and I 3 ; I 2 is intermediate. The very 

 heavy lower canine is scarcely a half longer than it is 

 thick as viewed on the inner side. Although broken, it 

 does not seem to be much recurved. The enamel covers 

 less than the upper half. 



.Pj is remarkable in having but a single root. It is un- 

 usual because, although its age is Lower Oligocene, it is 

 more advanced in its evolution than other species of the 

 Middle Oligocene. It is very small, almost vestigial, 



