THE PHOCID^. 



425 



like and can be closed at will, the eyes large and bril- 

 liant, and tbe auditory apertures small and devoid of a 

 pinna. The limbs are large, and their distal, longer than 

 their proximal, divisions. The fore limb is buried beyond 

 the elbow in the common integument, but the flexible 

 wi-ist allows the weight of the body to be supported by the 

 palmar surface of the manus. The hind limbs, on the 

 contraiy, are permanently extended and turned backwards 

 parallel with the taQ, which lies between them, and with 

 which they form a sort of terminal fin. When the Seal 

 swims, in fact, the fore limbs are applied against the sides 

 of the thorax, and the hinder moiety of the body being 

 very flexible, the conjoined hind limbs and tail are put to 

 the same tise as the caudal fin of a Cetacean. The Seal has 

 twenty dorso-lumbar vertebrae, of which five are himbar. 

 There are four sacral vertebrae, but only one of these unites 

 with the iHa. Eleven vertebrae enter into the formation of 

 the short tail. There are ten true ribs and nine stemebrae, 

 the manubrium being prolonged forwards into a long carti- 

 laginous process. 



The brain-case is smooth, rounded, and spacious, but 

 the cranium narrows rapidly in the interorbital region. 

 Its floor is remarkably flattened from above downwards and 

 very thin, the broad basi-occipital sometimes presenting a 

 perforation in the dry skull. The falx is partially, and 

 the tentorium is wholly, ossified. The occipital segment 

 is very large, and the supra- occipital advances between 

 the parietals, but does not separate them completely. The 

 alisphenoids are small and almost hoiizontal, and the syn- 

 chondrosis between the basisphenoid and presphenoid 

 persists. In all these respects the Seal's skull is strikingly 

 cetacean. In fact, if the supra-orbital processes were sawn 

 off, a Porpoise's brain-case would closely resemble a Seal's. 

 But the nasal bones and the parietals are large,, and the 

 ethmoidal region is very peculiar. The lamina perpen- 

 dicularis is largely ossified, and the vomer soon becomes 

 ossified into one mass with it. The two ethmoidal tur- 

 binals (or the superior and middle) are small and flattened, 



