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



do not at the present moment remember any facts tending to 

 shew that these very obvious differences may be merely sexual ; 

 and that they do not depend on difference as to age, I think has 

 been clearly made out by the preceding observations *. 



It may be observed, moreover, with a reference to the tusks 

 of the cranium now on the table, that there are no appearances 

 of permanent or other tusks behind these ; no vestiges of the 

 roots, or such other appearances as indicate their probable ulti- 

 mate replacement by others. The molar teeth correspond in 

 both jaws, and in the lower jaw of this cranium we find the al- 

 veoli for the reception of the imperfect rudimentary incisive 

 teeth formerly spoken of. These teeth are mostly present, but 

 not all, a circumstance which may either arise from some of them 

 having been thrown off, or by their having become encrusted 

 with bone. All this part of the jaw was covered with a dense 

 and almost horny semicartilaginous substance. A similar sub- 

 stance was found encrusting the palate above, and these sub- 

 stances seemed to me placed there, to supply the deficiency of 

 incisive teeth f . 



The dugong seems then to have originally, and, whilst yet 



* I observe, in a late number of the Annales des Sciences cTObservation that a 

 new species of fossil Hyaena has been established, merely from a slight variety of 

 form occurring in one of the molar teeth. 



J- There is rather a vagueness in what Sir E. HOME says about the milk-molar 

 teeth in an animal four feet eight inches long ; it seems reasonable to have expected 

 that the molar teeth in such an animal should have been proved to be milk-molar 

 teeth, by laying open the jaw and shewing the germs of the permanent ones below. 

 The same distinguished anatomist has, besides, from an accidental oversight no 

 doubt, given a representation of the upper jaw of a dugong, which must obviously 

 have been adult, there being two molar teeth on one side, and three on the other, 

 and has described this jaw as belonging to a young one, and has called these teeth 

 milk-molar teeth. 



