50 MAMMALIA. 



In the Museum of Practical Geology thei'o are two cheek teeth 

 of a Beaver from the Red Crag Nodule-bed ; one of these, from 

 Woodbridge, is a portion of a right upper premolar, about half 

 an inch long, which has all three of the external enamel folds 

 co-extensive with the tooth so far as this is preserved. The 

 second tooth (Plate V., fig. 16a, b) is from Boy ton, and is a 

 left lower premolar, much worn, and forming fangs at its base ; 

 the three inner enamel folds extend nearly to the fang, and in 

 this particular agree closely with a specimen of Castor fiber from 

 the peat of Essex ; the entire tooth, however, is smaller than the 

 corresponding tooth of the Essex specimen. Provisionally the 

 two Red Crag teeth are referred to Castor fiber. 



The specific identity of Castor europceus and C. fiber being 

 generally admitted, the latter and earlier name is now used. 



Castor fiber occurs in the Forest-bed and Red Crag Nodule- 

 bed in East Anglia ; it is also known in Pleistocene deposits both 

 in England and on the continent, and is now living throughout 

 the northern parts of the northern hemisphere. Gervais (Pal. 

 Fran9., Edit. 2, p.!20) would unite with this the Castor issiodorense, 

 C. & J., from the Pliocene of Mont Perrier. 



Castor veterioe, laneesteu. 

 Plate V., Figs. 13, 14, 16. 



Two upper cheek teeth and an incisor of a Beaver from the 

 Red Crag of Sutton, in the Whincopp collection (now in the 

 Reed Collection, York Museum) were described by Prof. Lan- 

 kester (Ann. Mag. Nat. Hist., Ser. 3, Vol. XIV., p. 355, 1864) as 

 Castor veterior. The cheek teeth {see Plate V., figs. 14, a, b, c) 

 are both left upper premolars, and were said to resemble those of 

 the Canadian rather than those of the European form, differing 

 chiefly " in the great length of the fang ;" . . . " the greater 

 width of the fossae of dentine between the enamel ridges, and in 

 the greater inward development of the large anterior [inner] fold 

 or lobe." Having made comparison with Beavers from the Fens, 

 I can corroborate what Prof. Lankester says ; but the variations 

 observable in different specimens of Castor fiber would have made 

 me doubt the validity of this new species, were it not for another 

 point of difference which seems of greater importance, and it is 

 that two of the three outer folds of enamel are only open to the 

 exterior for a short distance from the summit of the tooth ; while 

 in C fiber these folds are seen upon the exterior nearly to the base 

 of the tooth. 



The incisor tooth (Plate V., fig. 15, a, h), described by 

 Prof. Lankester, has all the characters of an upper incisor of 

 Beaver, and may very well be associated wii,h the two cheek 

 teeth. 



