268 Dr. J. E. Gray on Sea-hears. 



only because what they call hair-seals never have more than 

 a very small quantity of under-fur in the fur-season ; but, on 

 the other hand, many fur-seals at some seasons have only a 

 small quantity of tlie under-fur which is so long and abundant 

 at other periods. 



The form of the hinder opening of the nostrils, and the form 

 of its front edge, when only one or two skulls of a species were 

 examined, have been regarded as constituting a good character ; 

 but when an extensive series of the skulls of a single species or 

 of several species have been examined, that part is found to vary 

 considerably as to the width of its difierent parts, and espe- 

 cially in the form of the front edge. As far as my observa- 

 tions have extended, the hinder opening of the nostrils appears 

 to become narrower, and especially its front edge, as the ani- 

 mal becomes adult or aged ; and in the skulls of the younger 

 specimens it is broader, shorter, and the front edge is broader 

 and more truncated or straight, wdth only a slight rounding 

 at the sides. 



The position of the grinders, as regards the front part of the 

 zygomatic arch, is a good character for the distinction of the 

 species, especially if a series of skulls from animals of dilferent 

 ages, and from the same locality, of each species are compared 

 together ; and it is the same with the rooting of the grinders 

 themselves. But when adult skulls of the ditt'erent species are 

 compared together, the forms of the skulls are so altered, the 

 grinders generally so worn and altered by age, and their posi- 

 tion in diiferent species so similar, that tlie distinction of 

 the species then becomes more difficult. 



The Eared Seals (Otariad^e) should certainly form a distinct 

 family from' Phocidai and Trichechidas, of the suljorder Piiini- 

 pedia. They are distinguished by the distinct cylindrical 

 conch to the ears, tlic elongated arms and shins, the feet 

 fringed with a scolloped naked membrane ; the fore feet are 

 expanded into the form of a more or less triangular fin, and tlie 

 hind feet are elongated and narrow. The front toes gradually 

 diminish in size from the inner side ; and the hind toes are 

 nearly of equal length, the outer ones on each side being 

 rather the strongest ; they are all clawless. The fur in general 

 is provided with a more or less thick under-fur. They walk 

 on the lim])s, and rest with the hind part of the body bent 

 down and the legs directed forwards. 



The skull and skeleton are as distinct from those of the seal 

 as the external form. 



The female lies on her back to receive the caresses of the 

 male; and the young are born on the shore, and then gradually 

 tauG,-ht to swim. 



