CASTOKID.E— EUCASTOR— EUCASTOE TORTUS. 



4.49 



Table II. — List of specimens examined of Castor, fiber rar. canadensis— Continued. 



* In tho Museum of Comparative Zoology, Cambridge, Mass. * Variety fiber. 



Genus EUCASTOR Leidy. 

 EUCASTOR TORTUS Leidy. 



Cantor (Eueastor) tortus Leidy, Proc. Acad. Nat. Sci. Phila., 1858, -23. 



Castor tortus Leidy, Joarn. Acad. Nat. Sci. Phil., 2d ser., v, 1869, 341, 405, pi. xxvi, figs. 21,22; U.S. 

 Geol. Surv. of Wyoming, 1871, 363. 



This species was first described by Dr. Leidy in 1858, from remains 

 discovered by Dr. Hay den in the loose sands of the Niobrara River. These 

 remains consist of the greater portion of an upper jaw, containing portions of 

 the incisors and the three anterior molars on each side, and were redescribed 

 and figured by him in 1869. This fragment indicates an animal smaller even 

 than the common Marmot (Arctomys monax), and hence of much less than 

 half the bulk of the existing Beaver. The portion of the jaw described by 

 Dr. Leidy " consists of the under parts of both maxillary and intermaxillary 

 bones, which together are the diminished counterpart in form of the corre- 

 sponding parts of the recent Beaver. The incisor teeth likewise have the 



29 M 



