44 PACHYDERMATA. 



of the corresponding tooth of the Indian Elephant, but the ivory 

 segments are more vertical, thinner, and more approximated ; there 

 being about twenty-two plates in the space occupied by eighteen 

 or nineteen in the latter ; and the layer of enamel is still more 

 reduced in thickness. The disposition of the plates presents the 

 extreme degree of ' pectination' seen in the molars of any known 

 species of Elephant. The differences observable in the vertical 

 section are, however, so inconsiderable, that, if regarded in this 

 light merely, the Mammoth and the Indian Elephant might pass 

 for the same species. But when the grinding surface of the 

 crowns of their molars is examined, the transverse plates of 

 enamel in the Indian Elephant are seen to be thicker and very 

 closely undulated, with the flexures deeply wrinkled for the attach 

 ment of the stratum of cement ; while in the Mammoth the crowns 

 of the teeth are broader, the enamel plates are thinner and less 

 undulated, so much so that they are frequently described as being 

 transverse and straight. Such at least is the character of the 

 typical form of grinder in E. primigenius. This tooth measures 

 ten inches in length, being considerably under the size attained 

 by the largest specimens of the Mammoth. It has not been 

 deemed necessary to give a figure of the section of an inferior 

 molar, which differs in no respect from the upper, more than in 

 the case of the existing Indian species. 



These are the principal modifications in the construction of the 

 teeth of the Elephants. Although, at first sight, the molars 

 of E. insignis and E. primigenius appear to be very different, 

 the other intermediate forms constitute a series which estab- 

 lishes a passage between them. The species have been traced 

 in a retrograde order, from the simpler to the more complex 

 forms, with the object of making the descriptions more intelligible. 

 It is interesting here to observe how the existing species are inter- 

 calated: the serial order of structural development in the teeth 

 does not correspond with the order of succession of the species in 

 time. The extinct Mammoth exhibits the greatest amount of 

 complexity, constituting the terminal link of the chain ; and next 

 follows the existing Indian Elephant, interposed between two fossil 



