487 



are completed in succession : the tooth is gradually advanced hi position as its growth pro- 

 ceeds, and, in the existing Indian Elephant, the anterior plates are brought into use before 

 the posterior ones are formed. When the complex molar cuts the gum the cement is first 

 rubbed off the digital summits, then their enamel cap is worn away, and the central dentine 

 comes into play with a prominent enamel ring ; the digital processes are next ground down 

 to their common uniting base, and a transverse tract of dentine, with its wavy border of 

 enamel, is exposed ; finally, the transverse plates themselves are abraded to their common 

 base of dentine, and a smooth and polished tract of that substance is produced ; from this 

 basis the roots of the molar are developed, and increase in length to keep the worn crown on 

 the grinding level, until the reproductive force is exhausted. 



In the present grinder the enamelled summits of nine plates are exposed, and in the dif- 

 ferent degrees above described : in the ninth plate, only two of the mammilliform processes 

 appear : in the eighth a row of five such summits, the two middle ones of which are blended 

 together : in the seventh only the terminal ones of the transverse series continue distinct : the 

 first and second plates are worn down to their common uniting base of dentine. Two short 

 and thick fangs are developed from the part of the tooth supporting these plates. The base 

 of a common pulp-cavity has begun to be formed beneath the middle series of plates : the 

 last six plates have their hollow bases still free. In this tooth the characteristics of the 

 molar of au upper jaw are shown in the slight convexity of the grinding surface ; and, the 

 tooth being held with that surface downwards and the worn end forwards, the convexity of 

 the side to the right hand shows it to have come from the right side of the upper jaw. 



Hunterian. 



2771. A constituent denticle of one of the lamellae of a molar tooth. 



Presented by Prof. Owen, F.R.S. 



2772. A portion of a longitudinally divided constituent denticle of a molar tooth, 

 showing the pulp-cavity at its base ; the layer of enamel surrounding the 

 solid part of the dentine analogous to the crown, and general external coat of 

 rough cement. Presented by Prof. Owen, F.R.S. 



2773. One of the constituent plates of a molar tooth, consisting of five denticles 

 united together at their bases. 



Such detached plates offer a rude resemblance to a hand, and fossil ones of the Mammoth 

 (Elephas primigenius) may be found figured in some old works on Petrifactions, under the 

 name of ' Cheirolites,' as the fossilized hand of a monkey or child. 



Presented by Prof. Owen, F.R.S. 



2774. One of the constituent plates of a molar tooth a little more developed, and 

 the constituent denticles more extensively united; the pulp-cavity of the 

 common base has begun to be contracted. Presented by Dr. Henderson. 



