HALICORE. 365 



exterior of the great intermaxillary bones presents an unbroken 

 surface. In the female Dugong the growth of the permanent incisive 

 tusks of the upper jaw is arrested before they cut the gum, and 

 they remain throughout life concealed in the intermaxillary bones ; 

 the tusk is solid, is about an inch shorter and less bent than that of the 

 male ; it is also irregularly cylindrical, longitudinally indented, and it 

 gradually diminishes to an obtuse rugged point ; the base is suddenly 

 expanded, bent obliquely outwards and presents a shallow excavation. 



It is remarkable that the external wall of the socket is 

 always deficient opposite the expanded and distorted base of the 

 tusk of the female, and this vacuity occurs even in the young 

 Dugong of this sex, when the base of the growing tusk is near 

 the lower extremity of the deflected portion of the intermaxillary 

 bone ; but, as the base of the tooth ascends (or rather seems to 

 ascend in consequence of the elongation of the bone and the tooth), 

 the vacuity also ascends and becomes situated in the adult at the 

 upper part of the exterior of the deflected portion of the intermaxil- 

 lary bone. 



The solid tusks of the female Dugong were supposed by Sir E. 

 Home to be the deciduous or ' milk tusks' and to be the predecessors 

 of those of the male, which he held to be the permanent tusks, 

 and he suggested that the use of these projecting scalpriform tusks 

 was to detach sea-weeds — the food of the Dugong — from the rocks : 

 one can hardly, however, assign any important function in relation 

 to nutrition to parts which we now know to be limited to the 

 male sex. This hypothesis of Sir E. Home was first called in 

 question by Dr. Knox(l), who, having detected the supposed 

 deciduous tusks in the head of a nearly full-grown Dugong, 

 rejected the idea that they were deciduous teeth, observing that 

 no evidence had been given to prove the existence of deciduous 

 tusks at all in the Dugong(2). I have, however, discovered 



(1) Edin. Phil. Trans, vol. xi, p. 389. 



(2) " 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. — Sir E. Home seems, however, 

 to have observed the true milk-tusks, without recognising their nature, in the young female, 

 Dugong whose dissection he describes in the Philosophical Transactions for 1820, for he 



