380 



ORDERS OF MAMMALIA. 



milk-molars, as they have no predecessors or successors ; and 

 the last three are true molars. None of the molars, in fact, 

 undergo vertical displacement (prsemolars are present in the 

 extinct E. planifrons), but the whole series gradually moves 

 forward in the jaw ; and the place of each tooth, as it be- 

 comes gradually worn out, is taken by the tooth next behind 

 it in the series. As regards their form, the molars of the 

 Elephants are extremely massive, with an exceptional vertical 

 development, and composed essentially of transverse laminee 

 of enamel and dentine, more or less copiously united by a 

 coating of cement. The grinding surface of the tooth is 

 always crossed (fig. 662) by more or less numerous ridges. 



Fig. 662. — A, Left ramus of lower jaw of Elephas {Ewleplias) Indicus, viewed from above 

 (after Cuvier) ; b, Grinding surface of molar tooth of Elephas (Loxodon) A/riauius (after 

 Giebel). 



consisting centrally of dentine, surrounded with an external 

 layer of enamel, and these ridges are sometimes seen to be 

 obviously composed of a transverse and more or less confluent 

 series of tubercles. The triturating surface of the molars, 

 when worn down by use, is more or less flat, and the trans- 

 verse ridges of enamel and dentine give rise to various 

 patterns, which are highly characteristic of different species 

 of the genus. 



In accordance with the structure of the molar teeth and 

 the form and number of the dental plates, Dr Falconer has 

 divided the genus Elephas into three sections, which are 

 sufficiently useful to be introduced here, though it must be 

 admitted that they are to some extent founded upon an 

 artificial basis, and that there are so many transitional forms 



