296 Wortman — Studies of Eocene Mammalia, etc. 



fully described by Scott,* that if one can judge from appear- 

 ances, there will be little difficulty in supplying the deficiencies. 

 The formula of the specimen is I.f , C.-J-, Pm.|-, M.J-, but there 

 is reason to suspect that the senile condition of the individual 

 may be responsible for the presence of so few incisors in the 

 lower jaw. In the superior series there are three incisors indi- 

 cated upon each side, of which but a single one remains in 

 place in the jaw. The alveoli for the others are shallow and 

 apparently partially closed up, which would indicate that they 

 were to a certain degree caducous. They were, however, 

 implanted in the jaw in the ordinary way, and were very little, 

 if at all, procumbent. The canines are indicated by their large 

 elliptical alveoli, which penetrate deeply into the maxillae. 

 The first premolar is single rooted and follows immediately 

 behind the canine without diastema. The second is two-rooted 

 and had a crown in the unworn condition, composed evidently 

 of an anterior conical and a posterior basal cusp. The third is 

 likewise two-rooted, with a similarly constituted crown. The 

 fourth is three-rooted, and was therefore, a three-cusped tooth 

 of which there were apparently two subequal external and one 

 internal, being thus fully molariform. The two succeeding 

 molars are of the same size, and, as nearly as can be deter- 

 mined, their crowns have the same composition. The last 

 molar was considerably reduced, but the structure of its crown 

 cannot be made out. 



In the inferior series there is but a single pair of incisors, 

 but, as already remarked, the advanced age of the individual 

 at the time of its death may have had something to do with 

 this condition. Such a view is rendered all the more probable 

 by the fact that the tooth pertaining to the right side, which 

 still remains in place, lies close to the canine, while its fellow 

 of the opposite side, or at least what appears to be such, is 

 implanted almost directly in the middle of the alveolar border. 

 The canines, of which the right remains in situ, are of large 

 size and upright position. The crown of the one preserved is 

 badly worn, and, in consequence, is very blunt and rounded. 

 The wear resulting from contact with the corresponding tooth 

 in the upper jaw is postero-lateral, and hence normal, so that 

 it can be definitely stated that they had no such position as 

 Cope has described in Mesonyx lanius. With the exception 

 of the single-rooted, simple-cusped first premolar, all the suc- 

 ceeding teeth have the bicuspidate premolariform structure of 

 Mesonyx. The last molar is notably smaller than the rest and 

 is implanted well up on the sloping border of the coronoid. 

 This gives a peculiar and characteristic curved line of implanta- 

 tion. 



* Jour. Acad. Nat. Sci., Phila. 

 [To be continued.] 



