28 SEALS OF THE SHETLAND ISLANDS. 



contrast occurs in what Professor Bell relates of a Swedish 

 naturalist, M. Nilsson, mistaking the cranium of the Phoca 

 Grcenlandica for that of a differejit species. An untutored 

 Esquimaux having the perfect animals before him, could 

 never have fallen into such an error ; and yet this gentle- 

 man had long and assiduously studied the crania of seals, 

 and has given evidence of his industry and zeal. Amongst 

 the different parts of the skeleton, the teeth have been chiefly 

 appealed to, whence to extract specific characters. I have 

 been so long so familiar with the striking differences in ex- 

 ternal appearance and habits of the great and common seal, 

 that I have seldom looked at their structure with a view to 

 distinction, but chiefly in relation to their history or phy- 

 siology ; and it is not likely, after Professor Bell has de- 

 voted so much skill and attention to the subject, that an- 

 other will improve on what he has stated as the most marked 

 and permanent osteological characters he could detect. My 

 observations agree in the main with his. The cranial cavity 

 is smaller in proportion to the size of the animal and to the 

 bones of the face in the barbata than in the Small Seal ; the 

 bones generally are thicker and coarser ; the ridges and 

 prominences for attachment of muscles more projecting. 

 The cranial cavity is wider behind in the barbata, swelling 

 more laterally in the vitulina ; the distance from the 

 frontal bone to the end of the jaw much greater in the bar- 

 bata than the vitulina. In the former species considerable 

 differences exist in size, general form, and in the development 

 of particular parts in the crania of different individuals — 

 hardly any two being alike. The jaw of the male is longer 

 than that of the female ; and the bones of the nose are broader, 

 coarser, and more arched. The external aperture of the 

 nasal bones is in this species much greater than in the other. 

 In the teeth of the barbata, also, much diversity exists. In 

 some specimens the molars are very wide asunder, in others 



