OSTEOLOGY OF ANTARCTIC SEALS. 



21 



backwards and three-cusped, the central one being longest. In all but the first the 

 post-canines were double-rooted. 



In No. 43 the teeth are not so well developed, and in the upper jaw the left outer 

 incisor and caniue are broken. The dentition is not quite easily made out. There is 

 no fifth post-canine, but small sockets are to be observed ; hence we may presume that 

 they were present, having been partly fixed in the natural . state by the fleshy gum, a 

 condition pointed out by WEBER, BENNET, and WILSON (National Antarctic Expedition : 

 Natural History, vol. ii. p. 46). 



Again, in the lower jaw no central incisor is present, but the two halves of the jaw 

 have been disarticulated. On placing the two halves together, it would seem that no 

 room at all is left for central incisors. A comparison of the measurements of the two 

 lower and upper jaws between outer side of canines shows : 



No. 2. Upper diameter, 44 mm. 



Lower 30 

 No. 43. Upper diameter, 48 ,, 



Lower 26 



In No. 2, which has not been disarticulated, there is a fair amount of fibrous tissue, 

 so it is possible to explain the difference in diameters by the absence of this. Hence, 

 with the fibrous tissue in place in No. 43, room would be made for central incisors. 



Against this may be stated the fact that the upper central incisors are very feeble, 

 and, as the whole of the upper teeth are stronger than the lower, it is possible that the 

 lower central incisors may not have developed. 



Measurements of Skulls. 



The vertebral formula was : 



D 



Cd, 



'15 ^5 "3 ^"10' 



(BOY. soc. EDIS. TRANS., VOL. XLVIL, 191.) 



