E. T. Netdoii — TJie Great Beaver in the Thames Valley. 387 



grooved from end to end, and the inner side of the tooth, which 

 is not covered by enamel, is slightly concave. There is also 

 a groove along the enamel near its outer edge, but the outer edge 

 itself is rounded. The outer side of the tooth, uncovered by enamel, 

 is slightly convex with an indistinct depression along the middle. 

 The enamel of this tooth is everywhere rugose and granular, as 

 shown somewhat enlarged in Fig. 3. The only large rodent from 

 deposits of Post-Glacial age with which this tooth can be profitably 

 compared is the Beaver. Compared with the lower incisor of 

 a large specimen from the peat it is found to be absolutely longer, 

 even in its present imperfect condition, and to have a markedly 

 greater thickness. These differences of size would not alone suffice 

 to indicate even a specific difference, but are of importance when 

 taken in connection with differences in form and structure. The 

 enamelled front of the Beaver's lower incisor is almost flat, so that 

 the naturally worn cutting edge is straight and chisel-like. The 

 tooth above described has a rounded front, and consequently in 

 wearing would have a more pointed extremity. The enamel of 

 the Beaver's incisor is smooth and shining, not rugose and granular 

 like the present specimen. 



Lower right incisor tooth of Trogontheriimi Cuvieri from the Pleistocene of the 

 Thames Valley. Fig. 1, seen from the outer side, natm-al size ; Fig. 2, cross 

 section at a ; Fig. 3, enamel between a and b, enlarged two diameters. 



The lower incisor tooth of Trogontherium Cuvieri agrees with our 

 Greenhithe specimen in all those particulars in which the latter 

 differs from the Beaver; it has a similar rounded front, with rugose 

 enamel, a similar cross section, and is remarkable for its large size. 

 There can be no question as to the Greenhithe tooth being referable 

 to the genus Trogontherium, the range of which in time must now 

 be extended to the period of the High-Terrace gravels of the 

 Thames, and it must have been contemporaneous with the fauna 

 recorded by Mr, Stopes, which includes the mammals Eleplias 



