136 CARNIVORES. 



The Common Seal and the Greenland Seal. 



Genus Phoca. 



The common seal (Phoca vitulina) and the Greenland seal (P. grcenlandica) 

 may be selected as well-known examples of the genus Phoca, which is the only 

 genus in the family containing more than two species. All the members of this 

 genus differ from the grey seal by their smaller and more pointed teeth, but more 

 especially by the circumstance that each of the cheek-teeth, with the exception of 

 the first in each jaw, is implanted by two distinct roots, and has its crown composed 

 of three or four compressed cusps arranged in a line. In such a tooth there is one 

 large main cusp in the middle, which corresponds to the single cusp of the teeth of 

 the grey seal ; while in front and behind this are one or two much smaller cusps. 



The common seal, which is the only species in addition to the 

 grey seal ordinarily met with on the coasts of the British Islands, is 

 one of three nearly-allied forms, which in the young condition cannot always be 



Common Seal. 



SKELETON OF THE COMMON SEAL. 



satisfactorily distinguished from one another by colour alone. The three species 

 in question are the common seal, the ringed seal (P. hispidd), and the Greenland 

 seal. All these three species are much smaller than the grey seal ; the ringed seal 

 being the smallest of all. The latter species can always be distinguished from either 

 of the others by the greater length of the first digit in the fore-foot, which exceeds 

 that of the other toes. When adult, the ringed seal is blackish grey above, with 

 oval whitish rings, and whitish on the under-parts ; its usual length varying from 

 4 1 to 5 1 feet. The common seal, on the other hand, can be easily distinguished 

 from either of the others by its more massive teeth ; the cheek-teeth being very 

 broad and thick, and set obliquely and close together in the jaws, instead of being 

 placed in the same straight line, and separated from one another by distinct 

 intervals. It is, moreover, a relatively stouter-built animal, with a larger head, 

 broader nose, and shorter limbs. 



The adult of the common seal is very variable in colour, but the usual tint of 

 the hair on the upper-parts is some shade of yellowish grey, witli irregular dark 

 brown or blackish spots ; the under-parts being yellowish white, generally marked 

 with smaller spots of brown. The length of the male varies from 5 to 6 feet. The 



