46 



THE MAMMOTH. 



most favorable to progressive formation. This subdivision 

 of the grinder gives it an important advantage, for each 

 part is formed like a perfect tooth, having a bod}^ of den- 

 tine, a coat of enamel, and an outer investment of cement, 

 and each process almost complete within itself. The more 

 advanced and more abraded part of the crown is traversed 

 by the transverse ridges of the enamel investing the plates, 

 inclosing the depressed surface of the dentine, and sepa- 

 rated by the deeper channels of the cement. The fore- 

 Fig. 7. part of the tooth gives way first, for the 

 continued grinding on that part reduces 

 the enamel and cement which invest the 

 dental plates. This wearing away of the 

 forepart of the tooth does not entirely 

 unfit it for service, but was used for the 

 first coarse crushing of the branches 

 of a tree, and the succeeding part of the 

 tooth serves to still further grind the 

 food and reduce it to a pulp. Figure 7 

 represents the last molar but one. This 

 specimen was found in France by Lartet. 

 The tooth found near Zanesville, Ohio, 

 many years ago, is one of the best which 

 has been described. Its weight was over 

 seventeen pounds, and its length eight- 

 een inches. It was one of the set of per- 

 manent molars, of a light color, and 

 T. ,^- . ^. ■, , quadrangular in form. Of the four 



Penultimate Molar of ^ i . n 



the Lower Jaw. faccs the inferior IS oval m form, broad 

 in the middle and narrow at each extremity. The plates 

 in the surfiice are sixteen in number, formed of two layers 

 of enamel, displaying the remains of former plates, now 

 reduced to common dentine. The posterior and inferior 

 faces show the termination of undeveloped plates. The 

 superior border contains the roots, and the fourth face, or 



