MASTODON ANGUSTIDENS. 281 



the size of the tooth, which is six inches in length, shows 

 it to be the last but one in the molar series ; and the 

 convex bend of the grinding surface in the longitudinal 

 direction, proves it to have come from the upper jaw. 



The work of mastication first impresses the fore part 

 of the grinding surface, and the inner tubercles in the 

 upper molars are always worn lower than the outer ones. 

 By these marks, a Mastodon's grinder may be readily 

 referred to the jaw and the side of the jaw from which 

 it originally came, the tooth in question being the penul- 

 timate grinder of the right side of the upper jaw. It 

 must have belonged to a Mastodon that perished in the 

 vigour of youth, before the attainment of full maturity ; 

 for the two hinder pairs of tubercles had not been used 

 in mastication : and it could not, therefore, have been 

 shed in the ordinary course of dental change, since the 

 last molar tooth must still have been concealed in its 

 alveolar nidus of growth. 



The mutilated molar tooth of the Mastodon angustidens, 

 represented in figure 99, was likewise obtained by Mr. 



Fig. 99. 



Penultimate lower molar, Mastodon angustidens, Fluvio-marine Crag, Norwich, 



I nat. size. 



Robert Fitch, F.G.S., " from a crag-pit in the immediate 

 vicinity of Norwich." It is the penultimate molar of the 

 left side of the lower jaw, and had done good service to 



