510 CARNIVORES. , 



lobata, Fischer), the single molar is not developed in the upper jaw, 

 and the outer incisors above are not so large : in this species a thick 

 plicated cingulum belts the base of each molar, and developes a small 

 tubercle from its fore part in the molars of the lower jaw ; the crown 

 of the last molar above is notched. 



In the great proboscidian and hooded Seals {Cystophora, fig. 7) the 

 incisors and canines still more predominate in size over the molars ; 

 but the incisors are reduced in number, the formula here, is : 



2 2 1 1 3 3 2 2 



Incisors — ; canines — - ; premolars — ; molars -— 



1^—1 1"^J o^^o i^~Z 



30. 



All the molars are single-rooted and all the incisors are laniariform. 

 The two middle incisors above and the two below are nearly equal ; 

 the outer incisors above are larger. The canines are still more for- 

 midable, especially in the males ; the curved root is thick and sub- 

 quadrate. The crowns of the molar teeth are short, subcompressed, 

 obtuse ; sometimes terminated by a knob and defined by a constriction 

 or neck from the fang ; the last is the smallest. 



In the Walrus {Trichechus rosmarus) the phocal incisive formula 

 is transitorily represented in the very young animal, which has three 

 teeth in each intermaxillary bone and two on each side of the fore- 

 part of the lower jaw ; they soon disappear, except the outer pair 

 above, which remain close to the intermaxillary suture, on the inner 

 side of the sockets of the enormous canines, and seem to commence 

 the series of small and simple molars which they resemble in size 

 and form. In the adult there are usually three molars on each side, 

 behind the permanent incisor, and four similar teeth on each side of 

 the lower jaw ; the anterior one passing into the interspace between the 

 upper incisor and the first molar, and therefore being the analogue of 

 the molar. In a young Walrus's skull, with canine tusks eight inches 

 long, I have seen a fourth upper molar, (fifth including the incisor), 

 of very small size, about a line in breadth, lodged in a shallow fossa 

 of the jaw, behind the three persistent molars. The crowns of these 

 teeth must be almost on a level with the gums in the recent head ; 

 they are very obtuse and worn obliquely from above down to the 

 inner border of their base. The molars of the lower jaw are rather 

 narrower from side to side, than those above, and are convex or 



