228 PEOBOSCIDIA. 



together, prior to their basal confluence, by the external 

 cement ; this substance is generally more or less decom- 

 posed in fossil grinders, and the parts of the complex tooth 

 then become detached: a separate plate, with its digital 

 processes, offers a rude resemblance to a hand, and such 

 specimens have been figured by the older collectors of 

 petrifactions, under the name of " Cheirolites," as the 

 fossilized hand of a monkey or a child. The digital pro- 

 cesses of the last formed plates of the large molar tooth in 

 fig. 90, are shown at f, f, f: this figure well illustrates 

 the progressive development of the Elephant's tooth from 

 before backwards ; the formation begins with the summits 

 of the anterior plate, and the rest are completed in succes- 

 sion : the tooth is gradually advanced in position as the 

 growth proceeds, and its anterior plates are brought into 

 use before the posterior ones are formed. When it cuts 

 the gum, the cement is first rubbed off the digital summits ; 

 then their enamelled cap is worn away and the central den- 

 tine exposed ; next, the digital processes are ground down to 

 their common uniting base and a transverse tract of dentine 

 now the upper margin of the plate with its 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 of greater or less ex- 

 tent is produced. When the tooth has been thus reduced 

 to an uniform surface it becomes useless as an instrument 

 for grinding the coarse vegetable substances on which the 

 Elephant subsists, and is shed. 



The tooth figured (90) exhibits all the foregoing stages of 

 attrition : the common longitudinal base of dentine is ex- 

 posed at cT ; the continuous margin of a transverse plate at 

 d : and the digital summits of varying breadth, according 

 to the degree of abrasion, appear behind, and are followed 



