635 



3881. The upper jaw of a female Walrus (Trichecw Rosmarus). 



There is a minute molar behind each series of the four normal molars. 



Hunterian. 



3S82. The left maxillary and premaxillary bones of a young Walrus (Trichecus 

 Rosmarus}. 



The premaxillary shows the socket of the small incisor, together with that which forms the 

 first of the four normal grinders ; behind which there is a small circular socket of another 

 molar tooth. The premaxillary is here seen to rise and form part of the suture with the 

 nasal bone. The malar is completely suspended in the middle of the zygomatic arch. 



Hunterian. 



3883. The left premaxillary, and part of the maxillary with the socket of the canine, 

 of a large Walrus (Trichecus Rosmarus). 



The outer wall of this socket has been sawn off, showing the large, open, conical cavity for 

 the persistent pulp, into which stalactitic-like ossifications have shot from the apex of the 

 pulp-cavity, and the base of the socket. 



By a comparison of the dental system in the preceding extensive series of the skulls of the 

 Walrus, it will be seen that, in addition to the long canine tusk, four teeth are retained as 

 functional grinders on each side of the upper jaw, and that four similar grinders are present 

 in each ramus of the lower jaw. The first of the upper grinders, by its relation to the pre- 

 maxillary, must be held to be an incisor answering to f 3 of the typical series. There is a 

 smaller incisor anterior to this, which is less constant and less permanent, and answers to t 2. 

 The second, third and fourth are probably premolars : the smaller and less constant tooth 

 behind them may be the first of the true molars, m I, but the extent to which the normal 

 dental formula is manifested in this singularly modified Seal can only be determined by 

 examination of the jaws of the foetus. 



Hunterian. 



3884. The otosteals, called malleus, incus, and stapes, of a Walrus. 



Presented by Sir John Richardson, M.D. 



3885. The long canine, or tusk, of a Walrus. Hunterian. 



3886. The tusk of a Walrus. Hunterian. 



3887. The tusk of a Walrus. Purchased. 



3888. The tusk of a Walrus. Purchased. 



4 M 2 



