CHAP. IX.] 



TEETH : PINNIPEDIA. 



237 



20. 



£ and the molar, referred to above as characteristic of 0. stelleri 

 (see No. 342). 



The cases are grouped in an arbitrary collocation, according as 

 it seemed desirable that particular variations should be studied 

 together. In the sections dealing with premolars, Phocidae are 

 not separated from Otariida 1 . 



First Premolar. 



Ommatophoca rossii, an Antarctic Seal. Of this form only 

 two skulls are known, both in the British Museum. One of these 

 (B. M., 324, b.) has the arrangement usually found in Phocidse, 

 namely, five teeth behind the canines in each jaw, giving the 

 formula 



.2 — 2 1 — 1 5- 



i T i P + m 



2—2 



o 

 -5 



(on the analogy of other Seals p±, m\). The other specimen is 

 exceedingly remarkable (Fig. 55). In it the incisors and canines 



Fig. 55. Ommatophoca rossii, No. 320, teeth of the upper jaw. 



are as in the first specimen, but the first tooth behind the canines 

 on both sides in the lower jaw and on the right side in the upper 

 jaw, has a very peculiar form, having a deep groove passing over 

 the whole length of the tooth, on its outer and inner sides. These 

 grooves extend from the tip of the root along both sides of the 

 crown, and thus imperfectly divide each tooth into an anterior and 



