1908,] DR. FORSYTH MAJOR ON FOREST-BED MAMMALS. 631 



tlie only character by which the fossil i^emains can be distin- 

 guished from recent Beavers. Dr. Bosco some years ago * fully 

 described and figured the Valdarno remains ; he points out 

 another characteristic feature of this species, viz. the considerable 

 breadth of the incisors. Herein the fossil from East Runton 

 equally agrees with the Yaldarno specimens. 



Text-fig. 132. 



Castor plicidens Maj. East Runton Forest-bed. 

 Upper view of right lower molar series. 



(2) A second species of a Castor from the Forest-bed (B.M. 

 M 7025), likewise from the East Runton upper freshwater bed, 

 is represented by a left mandibular ramus, vertically split from 

 before backwards, only its outer half, and of the teeth m^ alone 

 (text-fig. 133) being preserved. It doubtless belongs to the same 



Text-fig. 133. 



Castor sp. East Runton Forest-bed. 

 Upper view of left mo. 



species as the specimens described from West Runton by Mr. E. T. 

 Newton ; as in the latter, the molar is slightly smaller than the 

 corresponding one of C. 2)liGidens ; the incisor, as apparent from 

 its alveolus, is narrower. The enamel of the molar is consider- 

 ably less plicated than in the latter species, although slightly 

 more so than is the rule in recent Beavers ; a moderate plication 

 of the enamel occurs, however, in old specimens of the recent 

 form (text-figs. 134, 135 B, 136 A). 



Text-fiff. 134. 



Castor fiber L. Peat deposit, England. 

 Upper view of right lower true molars. 



Mr. Newton has identified the West Runton Beaver with the 



* Palseontographia Italica, vol. v. (1899). 



