D N T G R A P II Y. 55 



of a young elephant. For, on opening into the cavity behind the teeth 

 already formed, we discover laminae with double plates, of different size and 

 thickness ; some of them being about a line thick, and presenting, in our structure. 

 specimens, a lateral surface of two and two-fifths inches by two and three- 

 fifths. They are composed of two layers, with fringed edges, and a cavity 

 between. These lamina? are afterwards united, and thus a number of them 

 are converted into a single tooth. 



The matter by which this union is accomplished is a hard substance, cement. 

 called the cement or crusta petrosa. The cement also unites the different 

 lamella?, when the tooth is completely formed, by extending from the base 

 of one lamina to that of another, just as it is continued from one ridge to 

 another of. the tooth of the Mastodon. Besides the cement, the tooth of 

 the elephant contains two other lands of hard substance : one is called the Dentine. 

 bone, ivory, or dentine, forming the basis of the tooth. The other consti- 

 tuent is the enamel, which, as before said, is seen to constitute the hard, Enamel. 

 white, prominent ovals of the Asiatic Elephant, and the lozenge-like 

 eminences of the African. These three parts are readily distinguished from 

 each other. The enamel is the most prominent part of the cutting surface 

 of the tooth ; the cement coats the exterior of the body of the tooth, and 

 glues together the lamina? ; while the dentine forms the basis of the fangs 

 and crown. 



The whole number of teeth in the elephant, according to the best of Number. 

 our present knowledge, is twenty-four, exclusive of the tusks. The existence 

 of five of these teeth on each side of each jaw, their regular and successive 

 development, we have the means of indicating by a series of specimens in 

 our possession and in other collections in this place. The sixth, probably 

 the last tooth, belonging to advanced age, is not included in any of these, 



