THE TRUE, OR EARLESS SEALS 



721 



ruses by the characteristics of the hind-limbs, which, as shown in the accompanying 

 figure, are permanently directed backward, and conjointly form a kind of rudder-like 

 organ. Then, again there is no trace of any external ear; and the neck is shorter than 

 in either of the two preceding families. As additional characteristics of the limbs, it 

 may be mentioned that the front pair are always smaller than the hinder, and that 

 the first digit or thumb of the former is always longer than the other digits; while 

 the whole of the digits are furnished with well-developed claws situated at their ex- 

 tremities. The hind-feet, which are incapable of the great expansion characteriz- 

 ing those of the eared seals, usually have all the digits armed with claws, and 

 generally want the long flaps of skin at their extremities, which characterize those 

 of the eared seals. The number of front or incisor teeth is variable in the different 

 groups; but there are constantly five pairs of cheek-teeth in each jaw, of which the 

 first four belong to the premolar series. In all the species the under surfaces 

 of both the fore and hind-feet are 

 covered with hair; while the fur 

 clothing the body is invariably 

 stiff and devoid of any woolly 

 under-fur. 



The true seals form a much 

 less homogeneous group than the 

 ared seals, and are arranged 

 under several distinct genera; the 

 total number of species being 

 about sixteen or seventeen, al- 

 though there is .still a certain 

 amount of doubt in some cases as 

 to whether some forms should be 

 regarded merely as local races or 

 as distinct species. The greater 

 number of the genera have but a 

 single species each, and in only one 

 of the genera does the number of 

 species exceed two. 



True seals occur along the shores of the temperate and colder portions of the 



globe; but the greater number are found in the Northern Hemisphere. Moreover, 



with the exception of the elephant-seals, the seals of the Northern 



and Habits Hemisphere belong to genera distinct from those inhabiting the 



Southern Hemisphere; and the whole of the Arctic species are generally 



distinct from those of the Antarctic regions. Nearly the whole of the true seals are 



characterized by their strongly-developed social instincts and their extraordinary 



affection for their young. In disposition they are, as a rule, gentle and submissive, 



offering no resistance when attacked by man; although the crested seal of the 



North Atlantic is an exception in this respect. Many of the species are accustomed 



to assemble in large flocks during the breeding season, while others are gregarious 



at all periods of the year. It is, however, only the elephant-seals that resemble the 

 4 6 



HIND- FLIPPERS OF RINGED SEAL OPEN (A) AND 



CLOSED (B). 



