43 



lares, which may be regarded as the permanent teeth, retain through 

 the greater period of life the wide conical cavity for their pulp, thus 

 resembling the grinders of the Edentata : the pulp of the last molar 

 becomes, in the progress of its development, extended in the antero- 

 posterior direction, and contracted transversely in the middle, so as 

 to give a sub-bilobed form to the mature grinder. Thus the molar 

 teeth of the Dugong succeed each other, as in the Elephant and true 

 Cetacea, in the horizontal, not in the vertical direction. The first 

 deciduous molares are shed before the deciduous incisors. They 

 are always much eaten away by the absorbents, especially about the 

 neck. 



" 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 ex- 

 amined, have I found incisors in the lower jaw ; they were two in 

 number, one in the corresponding socket of each ramus, which sock- 

 ets 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 de- 

 scribed in the jaws of the foetal Whale. The Dugong in which these 

 were found was eight feet in length ; the remaining six toothless al- 

 veoli in the anterior part of the lower jaw were also present, though 

 much shallower than those containing the teeth. In the other re- 

 cent heads examined by me, the alveoli in the deflected portion 

 of the lower jaw contained ligamentous processes given off from 

 the internal surface of the thick callous integument covering that 

 part of the jaw : they serve the purpose of fixing more firmly to 

 the bone this dense and almost horny plate, ■which is beset exter- 

 nally vidth short coarse bristles, and is doubtless used in scraping 

 and tearing off the sea-weeds and other alimentary substances which 

 maybe fixed to the rocks. 



" It is obvious that the different form and condition of the tusks thus 

 observed in the heads of Dugongs of the same size and age, might be 

 regarded as indicating a specific instead of a sexual difference. Dr. 

 Knox inclines to the former opinion * ; I have however adopted the 

 latter view, not hastily or hypotheticaUy, but as the result of a mi- 

 nute comparison of the forms and proportions of all the crania which 

 have come under my observation, and of which I have embodied the 

 principal results in the subjoined table. 



* This able comparative anatomist observes, " The tusks differ as much 

 in form in the two crania, as the tusks of the Asiatic Elephant differ from 

 those of the African one, and therefore naturab'sts would say, that these 

 animals must be specifically different." I hesitate, however, in asserting 

 this positively, and would rather say that it amounts with other data, such 

 as the belief, on the part of the Malays, in whose seas these animals reside, 

 that, to a great probability, there are two distinct species of Dugong now 

 inhabiting the Eastern Ocean. — loc. cit, p. 395. 



