some Remains of Uodents. 187 



inner folds of ^tt die out on the sides of tlie teeth a little below 

 the present grinding-suiface, so that, with a little fuitiier wear, 

 these folds would be converted into enamel " islets." ^4 is 

 in relation to ^n '-^ little longer antero-posteriorly than in 

 C. fiber ; its anterior surface is lightly furrowed by a weak 

 vertical sulcus — the last trace of a former more complex 

 condition of the anterior loop. 

 Dimensions : — 



C veterior. C.fiher. 

 mm. mm. 



Antero-posterior length of ^ 10 9-5 



"Width of j^4 behind 8 8 



Antero-posterior length of STi 7 80 



In the two upper premolars, from the Red Crag of Sutton, 

 upon which Sir E. Kay Lankester based his C. veterior"^, 

 Mr. E. T. Newton found 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 " f ; the lower teeth now 

 described present corresponding characters, and may there- 

 fore be referred to C. veterior. The differences in the number 

 of folds reduced peripherally in the individual teeth, viz., all 

 three inner in ^71, two outer in ^, and one inner in j^, are in 

 haimony with our experience of such reductions in other 

 rodents. 



In the relatively large size of jTTJ, and in the early conversion 

 into "islets" of the inner folds of lower and the outer folds 

 of upper cheek-teeth, C. veterior makes some approach den- 

 tally towards Trogonilierium ; in the latter all the enamel 

 folds are so reduced during wear, and in its later species there 

 is a great increase in the size of the animal. 



C. isbiodorensis, Croizet, is stated by Pomel J, Gervais§, 

 and Bo.sco |1 to be hardly or not at all different from C.fiher, 

 so far as it is known. C. prcrfibtr, Deperet^, from the 

 Pliocene of liousillon, is distinguished by its slender molars 

 and the absence of a third trochanter to the femur. To one 

 of these two forms the Red Crag beaver with persistent 

 enamel-folds, provisionally referred by Newton to C. fiber, 

 not improbably belongs. 



• Lankester, Ann. & Mag. Nat. Ili.'*t.(3) xiv. p. 355 (1864). 

 t Newton, ' Vertebrata of the Pliocene Depo&its of JJritain,' p. oO 

 (1891). 



J Pomel, ' Catalogue Methodique,' p. 20. 



§ Gervais, Zool. et Pal. Fram;. 1859, p. 20. 



II B08C0, ' Palajoutocrapbia Italica,' v. p. 89. 



in Deperet. M^m. SJc. G^ol. de Fraice, Pal^ontol. no. 3 (1890). 



