POL rJI A.STODOXTID.E. 



199 



The folio iv iny specimens are not specifically determined. 

 48399. Fragment of the left ramus of the mandible, showing the 

 three premolars, and a detached fourth lower premolar ; 

 from the Middle Purbeck of Durdlestone Bay. 



BecUes Collection. Purchased, 1876, 



Family POLYMASTODONTID.E. 



In the one known genus of this family the dentition is I. j, 

 The premolar is tubercular, and agrees in 



Pm. 



ILf 



structure with the true molars, although somewhat simpler; the 

 true molars are elongated antero-posteriorly, those of the upper jaw 

 having three ridges, mTl being longer than m72 and having six 

 tubercles on each side. The angle of the mandible is inflected ; the 

 huinerus has no entepicondylar foramen, and the astragalus is 

 without a trochlea ; the caudal vertebrae indicate a large tail. 



Fig. 32. 



Polt/mastodon taoensis. a, b, c, d. Right mandibular rainus ; from the Puerco Eocene of Ne\ 

 Mexico, e. Fragment of a maxilla. |. (From the ' Amer. Nat.') 



