236 MERISTIC VARIATION. [part i. 



premaxillae is different from that seen in other specimens of Phoca, 

 and, doubtless in correlation with the absence of the two upper 



Fig. 54. Incisors and canines of Phoca barbata, No. 318. 



incisors, the width of the premaxillae is considerably less than in 

 specimens having the normal dentition. B. M., 90. 8. 1. 6. 

 319. P« barbata: in left upper jaw are three normal incisors; but 

 on the right side the incisors have been lost. The alveoli, however, 

 shew plainly that only two incisors had been present. Of these 

 the outer one in size agrees with P, being a large alveolus equal to 

 that of i"3 of the other side, but the second alveolus, occupying the 

 place of i l and i 2 , is also a large alveolus, scarcely smaller than that 

 for R It appears therefore that in this specimen a single large 

 tooth stood in place of i 1 and %K A lower jaw placed with this skull 

 was normal, but it was not certain that it belonged to the skull. 

 O.M., 1724. 



Premolars and Molars. 



Normal arrangement. In Phocidae there are normally five 

 teeth behind the canines in each jaw, and according to the received 

 accounts, of these teeth 4 are premolars and one is a molar, giving 

 p f> m p T ne Otariidae on the other hand have generally p |, m f , 

 but both the two upper molars stand at a level behind that 

 of the lower molar, so that the posterior molar, w* 2 is placed so 

 far back that it meets no tooth in the lower jaw. Some of the 

 Otariidae, however, as 0. californiana, do not possess such a pos- 

 terior tooth, and have only m {. 0. stelleri is peculiar in the fact 

 that it also has only one upper molar, but this tooth is separated 

 by a large diastema from p 4 , and stands in the position character- 

 istic m 2 of the other Otariidae. Hence it may be supposed that ^ 

 is really absent while »& 2 is present. 



Amongst the cases will be found some of the presence in Pho- 

 cidas, especially Halichoerus, of an extra molar placed in the usual 

 position of »£ in the Otariidae. But lest any one should think it 

 manifest that this is an example of Reversion to the Otarian con- 

 dition, attention is called to cases of such an extra molar in the 

 Otariidse also. Similarly there are instances of absent molar in 

 those Otariidae which have m f , leaving m -j- ; and of these cases one 

 occurs in such a way as to leave the peculiar diastema between 



