HALICORE. 367 



tions. The socket containing this functionless tooth showed the in- 

 fluence of the stimulus of its presence by its greater depth and 

 smoother parietes, as compared with the other sockets, in which 

 the corresponding teeth had been wholly absorbed. The crown-end 

 of the latent incisor adheres to the thick gum in which it is buried : 

 this adhesion Sir E. Home describes as " gubernacula for the incisors 

 not yet completely formed :" he says, " these incisors enable the young 

 Dugong to crop the tender plants, but are no longer wanted when 

 the animal grows up ;" and adds, " this is a curious fact, and is 

 so far an approach to ruminating animals, whose incisors are only 

 in the lower jaw," loc. cit. p. 154. But the solidity, the exhaustion 

 of the formative matrix, and commencing destruction of the lower 

 incisors in the sockets of the lower jaw, which in Sir E. Home's 

 specimen had not cut the gum, prove that they were never destined 

 to come to use ; and the same thing must be inferred of those which 

 had disappeared. 



The truly remarkable instances already recorded in the Cetacea 

 of the manifestation and subsequent disappearance of the germs 

 of teeth, lead us to view without surprise this indication of allegiance 

 to a more general type, by which alone the phenomena of latent teeth 

 seem explicable. 



A comparison of the jaws of many specimens of different 

 sex and age has assured me of the accuracy of Cuvier's con- 

 jecture, that not more than twenty molar teeth are developed in 

 the Dugong ; viz., five on each side of both upper and lower 

 jaws : but these are never simultaneously in use, the first being shed 

 before the last has cut the gum. In the skull of a male Dugong 

 measuring fourteen inches in length, having the deciduous and per- 

 manent upper tusks in place, the first molar of the left side, lower 

 jaw, was shed, and the fang of those in place had suffered from 

 absorption : the second, third, and fourth molars were in use, but 

 the last presented its primitive obtuse tuberculate summit, and had 

 not penetrated the gum. In a female Dugong, whose skull was 

 fourteen inches eight lines long, and in which the deciduous tusks 

 were shed and the sockets obliterated, the last molars were in place, 

 and the conical summit worn down to the beginning of the transverse 



