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which are considered as incisor teeth. Of these, there are in the 

 upper jaw two abortive, which perish in their sockets, and two 

 which attain a great size. In the male, also, there are two tusks 

 in the lower jaw, one of which usually perishes before the adult 

 age, and the other attains a length of about twelve inches, or one 

 foot. As the number of the teeth and their character determine 

 the importance of any supposed extra tooth, it is necessary to 

 settle this point, and show it distinctly, which we are happily 

 able to do by two specimens. The teeth of the Mastodon are so 

 large and heavy, that the whole number can never be developed^ 

 nor exhibited in the same jaw at the same time. They are 

 naturally and necessarily divided into two sets, primary and 

 secondary. 



The primary teeth on each side of each jaw are three in 

 number, and are shown in a specimen of a jaw of a calf-masto- 

 don. The first of these is very small, and its crown has two 

 ridges. The second is somewhat larger, and has two ridges and 

 a half; it is generally said to have but two ; it will be perfectly 

 obvious to you, that it has more nearly three than two, thus 

 approximating the M. angustidens and longirostris, in which 

 this tooth has three ridges. The third tooth is larger than the 

 second, and has three crown ridges. These three teeth consti- 

 tute the first series, the primary, or milk-teeth. 



The second series, or permanent molars, so called, though 

 they are not all entitled to this epithet, are three in number. The 

 first of these has three ridges, like the last named, but differs 

 from it in being larger. The second tooth in the series is still 

 larger than the first, and contains the same number of ridges. 

 The third tooth in the second series is larger than the preceding, 

 contains four ridges and a talon, or heel ; in the lower jaw, occa- 

 sionally, it has five ridges. This completes the entire set of one 

 side of one jaw, and shows us, in the whole, in the two jaws, 

 twenty-four teeth. This is the greatest number which has ever 

 been known to anatomists ; neither Cuvier, De Blainville, Hays, 

 nor any other anatomist, has seen an instance of any additional 

 tooth in the Mastodon giganteus. Professor Owen, in regard to 

 the M. angustidens^ and Dr. Kaup, in regard to the M. longirostris, 

 have shown, that there is in the upper jaw a small vertical tooth, 



