COMMON SEAL. 241 



molar-teeth, by which the inner posterior margin of one 

 is brought in contact with the outer anterior margin of 

 the next behind it, was pointed out in our first edition 

 as being not less striking than distinctive. Since then 

 Mr. Ball has expressed the opinion that this character is 

 not to be depended upon, it being a mark of youth and 

 disappearing " long before the skull attains its maximum 

 size " (Trans. Roy. Irish Ac., v. VIII.) ; but we still believe 

 that it will be found to be characteristic at all ages, 

 although it is certainly more marked in young than in 

 very old animals. In the structure of the skull, also, 

 well-marked features will be found, of which we may 

 mention the following : The posterior margin of the 

 palatal bones is deeply and acutely notched, affording 

 a good character to distinguish the skull from that of 

 Ph. barbata and Ph. grcenlandica ; and the posterior pala- 

 tine foramena are situated on the maxillse, and not on the 

 palatines or on the suture as in Ph. hispida. Another 

 striking peculiarity is in the form of the intermaxillary 

 bones, the ascending processes of which do not run up to 

 a point along the outer margin of the nasals, as in the 

 other members of the genus, but are truncated above, 

 and either do not touch the nasals at all, or are in con- 

 tact with them at one point only. These characters we 

 believe to be quite constant, and they will be easily 

 understood by a comparison of our figures of the skulls 

 of the various species. In external form and markings, 

 it would be difficult to point out definitely any one 

 peculiarity by which this species could be unhesitatingly 

 separated from its nearest allies. 



The Common Seal is strictly littoral in its habits, 

 frequenting the coasts of both sides of the North 

 Atlantic, but avoiding the ice of the open sea. It is 

 common in Spitzbergen, Greenland, and Davis Straits ; 



I I 



