CHAP. IX.] 



TEETH : PINNIPEDIA. 



239 



gaps normally existing between the teeth in this species there is no 



crowding. 



Between these two teeth there are slight differences of 



Fig. 57. Phoca grcenlandica, No. 324. Left and right profiles. 

 This figure was kindly drawn for me by Sir J. J. Lister. 



325 



form, and the posterior is rather the larger. On both sides "^ is in 

 place and at the same level. Both the two teeth in place of p^ bite be- 

 tween p* and m} of the lower jaw. On the right side pf is normal and w* 1 

 is also normal but ^ is a very large and thick tooth, and its main cusp 

 is cloven, giving it the appearance of imperfect division into two. In 

 this case therefore F 4 on the one side may be supposed to have divided 

 into two perfect and nearly similar teeth, while on the right side this 

 division is begun but not completed. Leycl. M. 



Otaria ursina <£ : supernumerary premolar in left upper jaw. 

 This is a curious case. The right upper and both lower jaws are 

 normal. On comparing the left upper series of 7 teeth with the right 

 series which has 6 normal teeth, it is seen firstly that the two molars 

 of each side are alike in form and stand at their proper levels (Fig. 58). 



Fig. 58. Otaria ursina, No. 325, seen from left side. 1, 2, 3, 4, first to fourth 

 lower premolars ; 5, lower molar. 



Next, the two posterior premolars of each side (p^ and p^) agree so 

 nearly that there is no reasonable doubt that they are not concerned 

 in the variation. Anterior to this there is difficulty, for whereas p 1 

 and p 2 are normal and in place on the right side, there are three teeth 

 on the left side to balance them. These three teeth moreover are so 

 nearly alike that it is impossible to say that either of them is 



