394 DR KNOX on the Dentition of the Dugong, and on the 



rior part of this bone slopes greatly, and is of vast strength, and 

 there are cavities for eight rudimentary teeth, which teeth, how- 

 ever, are not present. It will be quite obvious to every one, 

 that the teeth may have been lost by maceration, or have been 

 intentionally removed, or accidentally dropt out ; to me it seems 

 probable that they occasionally remain in the jaw during the 

 whole period of the animal's existence. Upon the whole I do 

 not reckon this a question of any moment. The right tusk of 

 the narwal (which is an incisive tooth) remains always im- 

 bedded in the jaw, and seldom shews itself even beyond the 

 gums, and, were it not for this, I should imagine, by what we see 

 take place in man, that the alveolar cavities would be absorbed 

 and disappear, and thus cause a great loss of depth and strength 

 in this part of the jaw. If we apply this reasoning to the jaws 

 and small rudimentary incisive teeth of the dugong, we shall find 

 the natural conclusion to be, that they probably get entangled 

 in the alveolar cavity, and may possibly thereby prevent its ab- 

 sorption and disappearance, which, according to the physiologi- 

 cal laws prevalent in other animals, would most certainly take 

 place, were the teeth entirely removed. Those who talk of the 

 filling up of the alveolar cavities, after the removal of the teeth, 

 either by a natural process or otherwise, employ a language ex- 

 ceedingly incorrect, and at total variance with the whole history 

 of dentition, and the changes which take place in the maxillary 

 bones of animals, from a variety of causes. 



Without pretending, therefore, to consider it as a view finally 

 settled, I deem it merely probable that the incisive teeth in a 

 rudimentary state are retained, and lodged in the alveolar cavities 

 of the lower jaw-bone, throughout the life of the animal, for the 

 reasons assigned. Should it be afterwards shewn that an oppo- 

 site law prevails in the dugong, to what takes place in other ani- 

 mals ; should it hereafter be shewn that the alveolar processes 

 of the maxillary bones can and do retain all their depth and 



