135 



It presents a more elongated and curved form, and the grinding sur- 

 face is slightly concave and adapted to the convexity of that of the upper 

 tooth. The same gradational state of the development of the tooth 

 from the posterior separate cylindrical or digital processes of the plates 

 to their union at the base of the plate, and the blending of the plates 

 themselves at the base of the crown, the development of fangs from, and 

 the wearing down of the plates to, this base, are as instructively shown in 

 this as in the upper grinder. The crown of this lower molar is divided 

 into twenty-seven plates, twelve of which have come into use : in the pos- 

 terior of these the middle mammillary process is abraded : the fourth in 

 advance exhibits five mammillary processes, the three middle ones being- 

 nearer to each other than to the two lateral ones, the next in advance has the 

 three middle processes worn down to a single cavity. As the lamellae ad- 

 vance they increase in breadth, by the widening of the lateral mammillary 

 processes which are worn down to their broader part : in the three anterior 

 plates the lamellae are blended together into one depression. The enamel 

 capsules of the ivory plates are strongly plicated like a frill. 



The length of this molar tooth, following the curve on its outer side, 

 is one foot seven inches : the posterior and last-formed plates are folded 

 upwards and laterally upon the rest, their sides being parallel to the 

 grinding surface of the tooth. 



From British drift or pleistocene beds. Hunterian. 



567'. An upper molar of an Indian Elephant (Elephas indiciis, Cuv.), for com- 

 parison with No. 562. It differs from the fossil in being- relatively 

 narrower or of less diameter transversely. The lamella? are less deeply 

 cleft, and the digital or mammillary processes of their summits are shorter. 

 The length of the tooth is twelve inches ; that of the grinding surface is 

 five inches ; its breadth two inches nine lines. The crown is divided into 

 twenty-two plates, of which nine have come into use. Hunterian. 



567 2 . A lower molar of an Indian Elephant, for comparison with No. 567- It 

 is shorter in proportion to its depth, is divided into relatively fewer 

 plates, and these are less deeply and less numerously subdivided into 

 digital processes. The length of the tooth is twelve inches, and it is 



