488 Bulletin American Museum of Natural History. [Vol. XVI, 



Skull. The skull is fully twice as large as that of Phoca vitulina, from 

 which it differs mainly, so far as general features are concerned, in its 

 massiveness. The teeth are essentially the same as in the P. vitulina 

 group (Phoca restr.) , in which the dentition differs from that of the Pusa 

 and Pagophilus groups in the large size of the crowded and more or less 

 obliquely implanted teeth, the teeth in both Pusa and Pagophilus being 

 small, placed in a straight line and separated by broad diastema. P. 

 stejnegeri agrees with all of the other known Pacific and Bering Sea seals 

 of the genus Phoca in the posterior extension of the premaxillae to the 

 side of the nasals, but differs from them in the possession of a groove in 

 front of the infraorbital foramen for the maxillary nerve, which runs for- 

 ward from the infraorbital foramen to a point opposite the middle of 

 pm 3 . As this deep, strongly denned groove is present in all of the four 

 skulls of P. stejnegeri available for examination, and is uniformly absent 

 from some thirty or more skulls of P. vitul-ina, P. richardii, and P. ocho- 

 tensis, it appears to be a character of some weight. 



Dentition. Another feature of importance is found in the character 

 of the teeth, the superior premolars 2-4 being 4-cusped in the type skull, 

 and apparently so in the two other adults, in which, however, the teeth 

 are too much worn for satisfactory examination. In the young (female ?) 

 skull (No. 21311), these teeth have the same conformation as in P. vitu- 

 lina. 1 In the lower jaw pm s . 4 are strongly 4-cusped, as is also the molar 

 in two of the three adult skulls; in the third the molar on both sides of 

 the jaw has been lost. In the lower jaw of the young skull pm 2 . 4 on both 

 sides, and the molar on the right side, are distinctly 4-cusped, but the 

 molar on the left side has only three cusps. In other words, P. stejnegeri 

 seems to be separable from the P. vitulina group by the quadricuspid 

 instead of tricuspid superior molariform teeth. 



The premolars have the same oblique position as in P. vitulina, vary- 

 ing greatly, however, in this respect with the individual. In the three 

 adult skulls from Bering Island only pm 2 is obliquely implanted, but in 



1 The crowns of the teeth in the skulls Nos. 38011-38013 and No. 114652 have crum- 

 bled away, and these skulls therefore throw no light on the number of cusps and form 

 of the teeth. 



