MUSEUM OF COMPARATIVE ZOOLOGY. 



165 



Dentition 



I. f, C. 



METAM JTNODON, gen. nov. 



\, Pra. f , M. |. Upper and lower canines obliquely 

 placed, the latter fitting somewhat internal to the former when the jaw is 

 closed. The first upper premolar wanting; the second, third, and fourth pre- 

 molars are of the molar pattern. Post-glenoid and post-tympanic processes 

 widely united. 



Figure 7. — Skull of Metamynodon planifrons, in side view, about one sixth natural size. 



Metamynodon planifrons, sp. nov Specific characters. First upper molar 

 with an incomplete internal cingulum. Lower median incisors small. The 

 molars greatly exceeding the premolars in size. 



This genus is represented by a single skull in fine preservation, and the 

 anterior portion of the left mandibular ramus. The latter specimen was found 

 some little distance from the skull, but for many reasons may be safely placed 

 with it. The canine-incisor formula is the same, and the diameters of the 

 canine fangs are similar. There is one less premolar, but the molar-premolar 

 series as a whole has the same antero-posterior length. 



Metamijnodon is evidently a highly modified .successor of Amynodon, of about 

 double its size and strength. The dentition is reduced by the loss of one upper 

 and two lower premolars. The pattern of the premolars presents a slight pro- 

 gression in the complication of the transverse crests of pm^ ; but as a series 

 they show a decided retardation of growth as compared with the molars which 

 assume very large proportions. The mandibular symphysis is relatively 

 much narrower. The sagittal crest is still more powerful. The skull is modi- 

 fied by the unusual shortening of the facial region, and the flattening of the 

 cranium and broadening of the zygomatic arches, but without the develop- 



