ODONTOGRAPHY. 75 



This concludes the description of all the teeth, so far as we have had 

 an opportunity of observing them. 



Some authors have thought that there might be an additional premolar Additional 



Premolar. 



tooth, situated at the root of the second milk-tooth, in the Mastodon Gigan- 

 teus, as was discovered by Cuvier in the Mastodon Angustidens, and by 

 Kaup in the Mastodon Longirostris. 



In some of the specimens of the Mastodon Giganteus within our 

 knowledge, the lower jaw has been carefully examined, and the supposed 

 locality of this tooth explored, without the discovery of any such vertically 

 situated tooth, or any vestige pf its former existence. An opening was 

 made, by Prof. J. B. S. Jackson, in the jaw of a calf Mastodon, belonging to 

 the collection at Cambridge, as represented in Plate II. The specimen con- 

 tained the milk molars, and the' first small six-pointed molar; but there was 

 not found the slightest appearance of an imbedded tooth between them.* 



In the jaw of another young Mastodon, an examination was made for 

 the purpose of determining the same question. This specimen consisted 

 of the right half of the lower jaw, containing two developed teeth, a posterior 

 socket from which a tooth had fallen from decay of the bone, and an ante- 

 rior socket from which a tooth had been shed in the process of dentition. 

 The two existing teeth were both three-ridged, the anterior, of them being 

 the first small three-ridged molar : the socket in front of this had contained 

 the second two-ridged milk molar. An incision was made in the bone 

 below the interstice of these teeth, the supposed situation of the vertical 

 premolar; but no trace of any such tooth, or any socket that could have 



% "Proceedings of Boston Society of Natural History," vol. ii. p. 140. 



