THE PROBOSCID.E, OR ELEPHANTS. 231 



cases of enamel which are filled with dentine and 

 joined into one mass by cement. This account of 

 the formation of the tooth, which is universally 

 accepted by descriptive zoology, is, however, as we 

 shall see, not correct, and very unnecessarily makes 

 the gap which does exist between the Elephants 

 and the other plant-eaters appear greater than 

 need be. 



Even Cuvier distinguished among the Elephants 

 a group of fossil trunk-bearers, perfectly of the 

 elephant type, but with a more complete dentition ; 

 the molars, although less large than those of the 

 elephants, being characterised by nipple-shaped 

 eminences or tubercles in pairs, forming a number 

 of transverse ridges. Cuvier called the genus 

 Mastodon. 1 A mastodon tooth of this kind (Fig. 

 40) presents nothing specially striking apart from 

 its often remarkable size. The crown, however, is 

 distinguished by the extraordinary strength of the 

 connecting layer of enamel which does not pene- 

 trate in folds into the interior. Now, as three 

 molars of this kind with huge tuberculated crowns 



1 The most important contributions on this subject are : 

 Vacek, ' Ueber osterreichische Mastodonten und ihre Beziehungen 

 zu den Mastodonten Europa's,' Abhandlungen der geologischen 

 fteichsanstalt, vii. : most admirable also is the chapter on the 

 Elephantoides ' in Gaudry's Mammiftres lertiaires. 



