344 Dr. J. E. Gray on Seals. 



appears to diminish, or, rather, not to be extended as the jaw 

 becomes thicker in front, which it does in the adult animal. 



In the skull of the adult animal, it no longer forms a pro- 

 jection on the inner side of the lower edge of the jaw; the jaw 

 being much thicker and more substantial, it forms only a slightly 

 marked keel on the middle of the lower surface of the jaw, 

 separated from the rest of the jaw by a slight groove on its 

 inner side. 



The extent of this dilatation in the young animal affords a 

 character for the separation of the young animals of the dif- 

 ferent species. Thus, in the young CciHocephalus vitulinus, 

 the dilatation only extends to a line even with the third lower 

 grinder ; in Pagomys foetidus it extends to a line even with 

 the fifth or last lower grinder, and it is wider and more deve- 

 loped in the latter than the former. The ramus of the lower 

 jaw in this genus is so oblique and directed backwards, that 

 the angle on the hinder part of the lower edge is in a line 

 considerably in front of the upper part of the compressed pro- 

 cess in front of the condyle. (See Proc. Zool. Soc. 1864, p. 29, 

 f. 3 ; Cat. Seals & Whales Brit. Mus. 1865, p. 28,_f. c.) 



Though it is impossible to determine the species of Seals 

 with any certainty without the more careful examination and 

 comparison of the skulls, yet it is by no means impossible that 

 two or more specimens which are very distinct in external 

 characters, manner, habit, voice, &c. may have very similar 

 skulls, or skulls so alike that, when they are compared in a 

 museum, they may be regarded only as individual or acci- 

 dental variations of the same species. 



The form of the hinder edge of the palate seems to be less 

 liable to variation in the Earless Seals [Phocidce) than in the 

 Eared Seals or Sea-bears, at least as far as I have been able 

 to observe in the skulls of these Seals in the British-Museum 

 and other collections. 



The earless Seals {Phocidce) are distinguished from the 

 other Pinnipedia thus : — A small perforation for the ear, with- 

 out an external conch. Eyes large. The feet hairy, more or 

 less clawed ; fingers short, curved, webbed, clawed, forming a 

 well-formed webbed foot ; the toes unequal, the three middle 

 shorter, forming a broad triangular foot when expanded and an 

 elongated paddle when contracted ; the palm and soles hairy. 

 The hind limbs are folded together, and are produced outwards 

 behind the body, when on land or in the water. Walking 

 on land by the action of the abdominal muscles. Testicles 

 enclosed in the body. Skull and skeleton very distinct from 

 those of Otariadee in external form ; skull without any, or only 

 a rudimentary postorbital process. 



