190 



Annals of the Carnegie Museum. 



of its greater age, longer than the premolar. It appears to be open 

 below and not to have completed its growth. It is very doubtful if 

 this tooth would be shed during the lifetime of the animal. It had 

 not yet come into use, at least it is not worn, though it projects some 

 distance above the alveolar border. M3 was just erupting. Evidently 

 the two temporary molars and the two permanent ones were about 



equal in length and width. 



Measurements. 



Mm. 



Depth of ramus under last molar II 



Length of dental series 13 



Antero-posterior diameter of immature permanent jiremolar 6 



Length of dm^j and mSy and ^ each 3 



Same beds as the preceding. 



Myi.agaulus sp. 

 No. 723. Fig. 28. 

 This specimen, which is a portion of a lower jaw, has lost the pris- 

 matic premolar, which judging by the inner portion of the alveole, 



Fig. 28. My/agaitliis} (^o. •J2T,). Lower Madison valley. ^ natural size, a, 

 portion of jaw showing alveolus of F^j , dpj ? and M^ ? M^ ? ; b, crown view of same, 

 Pj ; nl, alveolus of permanent premolar, dp^ temporary premolar. 



was proportionally as large as in the specimen just described. The 

 last temporary premolar is much reduced, as if by partial absorption, 

 as in the specimen of J/, froximus (No. 842). Its antero-posterior 

 is half its transverse diameter. The crown is nearly worn down to 

 the roots. Mg^ is not so high as in M. pristimis. M3 is still lower. 

 Both the molars might be shed in old age. 



