306 Zoological Society. 



deciduous teeth. This opinion of Sir Everard Home was first called 

 in question by Dr. Knox*, who, having detected the supposed de- 

 ciduous tusks in the head of a nearly full-grown Dugong, rejected with 

 great justice the opinion of Home, that they are deciduous teeth ; 

 and he truly observes, that no evidence had been given to prove 

 the existence of deciduous tusks at all in the Dugongf. 



" I need hardly observe that the tusks of the Dugong, being im- 

 planted in the intermaxillary bones, are to be regarded, like the tusks 

 of the Elephant, as incisors. Now both sexes of the Dugong, as of 

 the Elephant, do, in fact, possess deciduous or milk-tusks, but they 

 are much smaller than the female permanent tusks or supposed de- 

 ciduous teeth of Home. 



" In the skull of a male Dugong which had molares ~|, the sock- 

 ets of the deciduous incisors were obliterated, and the points of the 

 permanent ones projected from their sockets. In only one out of 

 Seven crania of the Dugong which I have examined, have I found 

 incisors in the lower jaw ; they were two in number, one in the cor- 

 responding socket of each ramus, which sockets were much deeper 

 than the rest. These teeth were smaller and more bent than the 

 deciduous incisors of the upper jaw. They are obviously analogous 

 to the rudimental teeth which have been described in the jaws of 

 the foetal "Whale. 



" The short and thick neck, fin-like fore-legs, want of hind-legs, 

 caudal tegumentary fin, smooth, naked, and almost hairless integu- 

 ment, are all modifications of external form, by which the Dugongs 

 and Manatees are adapted to play their part in the waters : but the 

 kind of part which they are to play in that element depends on or- 

 ganic characters which mainly if not exclusively reveal their true 

 affinities. Now we have seen that the whole of the internal struc- 

 ture in the herbivorous Cetacea differs as widely from that of the 

 carnivorous Cetacea, as do their habits : that the amount of varia- 

 tion is as great as well could be in animals of the same class, exist- 

 ing in the same great deep. The junction of the Dugongs and 

 Manatees with the true Whales cannot therefore be admitted in a 

 distribution of animals according to their organization. With much 

 superficial resemblance they have little real or organic resemblance 

 to the Walrus, which exhibits an extreme modification of the am- 



• Edinb. Phil. Trans, xi. p. 389. 



f " The milk-tusks of the Dugong have never been seen by any one ; 

 that is, I have not heard of the existence of any preparation showing the 

 germs of the milk or permanent teeth, together or in succession." — Dr. 

 Knox, loc. cit, p. 398. 



