32 Wortman — Studies of Eocene Mammalia in the 



The third molar differs from the two in advance of it in 

 showing a still further reduction of the anterior cusp of the 

 trigon, which can hardly be said to be distinct, as well as the 

 presence of a w T ell-developed third cusp and a more elongated 



121 



122 



iii2'C< r pi p2 pa mi mz ma 



Figure 121. — Left lower jaw of Omomys Carteri Leidy ; showing the 

 alveoli for front teeth ; external view ; two and one-half times natural size ; 

 drawn from two specimens. 



Figure 122. — Crown view of the preceding figure ; two and one-half times 

 natural size. 



heel. It is also noticeably narrower, and in many respects dis- 

 tinctly smaller, than the anterior molars. The heel has a large 

 submedian cusp, which stands a little nearer to the inner than 

 to the outer side of the crown. 



From - the great number of additional specimens of this 

 species in the collection, it is possible to learn the exact dental 

 formula of the lower jaw, which is shown in the accompany- 



123 



Figure 123. — Crown view of three superior molars of Omomys Carteri 

 Leidy (type of Palceacodon vagus Marsh) ; four times natural size. 



The cingular cuspule internal to the main antero-internal cusp of the first 

 molar is worn away in the specimen, and has not been indicated by the 

 artist with sufficient distinctness. The external cusps are more flattened 

 externally than is shown in the drawing. 



ing cuts, figures 121 and 122. There is no specimen in which 

 the crowns of the incisors, canines, or first (second) premolar 

 are preserved, but that of the second (third) is shown in sev- 

 eral examples. Its chief characters are as follows : 



There is a single high pointed cusp, which rises consider- 

 ably above the remaining teeth ; there is no internal nor ante- 



