THE INTERNAL ANATOMY OF THE MARINE CARNIVORA. 



211 



UPPER SURFACE OF BRAIN OF OTA1UA. 



(After Murie.) 



short and simple-fanged, the canines themselves, or, as they are more commonly termed in this animal, 



tusks, being of inordinate length and strength. In the Otariidse, the canines, though themselves of 



good size, are small in comparison with those of the Morse 



tribe, while the incisors and single-rooted molars are more 



conical and prominent. The dentition of the Phocidse 



varies considerably, in some the occasionally double-rooted 



molars acquiring a tuberculate, in others a saw-like or 



serrate character, while the incisors are notch-ci'owned. 



The bony cavity for the eye is open behind ; the facial 



region is less prominently produced than in some of the 



feline Camivora. The region of the brain-pan is relatively 



full, while the skull, as a whole, is elongated and flat. In 



youth, the cranium of the Pinnipedia has a predominating 



brain area, and the entire bony surface is smooth and 



featureless. As age advances, however, in certain of the 



genera at least, the relation of parts changes, and the face 



acquires prominence, while great bony crests arise on the 



summit and back of the head. The tongue does not possess 



the spines met with in the Cat tribe, though the surface 



is roughish. In the Seals, but not in the Walrus, the tip is 



slightly cleft. The stomach is single-chambered. The in- 

 testine is considerably longer than in the Felidse, averaging 



fifteen times the length of the body, or thereabouts. The 



glands of the internal coat in some of the tribe are very exten- 

 sive, and co-ordinate with the excessively rapid digestion. 



A curious point in connection with the veins entering the liver 

 is their enormous dilatation. This, by some writers, has been 

 regarded as the means whereby the animal is enabled to remain 

 submerged, the blood being held in these reservoirs instead of 

 passing on towards the heart and lungs to be aerated. But whether 

 this peculiar disposition of the blood-vessels is necessarily connected 

 with diving powers, up to the present time has not been satisfactorily 

 decided. Whatsoever the relation between structure and habit in 

 this respect, it has been observed that the staying-power of the Seal 

 tribe under water increases from youth to age. In the Pinnipedia, 

 the lungs, relatively, are capacious, the animal rising to breathe air 

 at intervals from ten minutes to half an hour or more, when at the 

 surface taking a long and deep inspiration. The nostrils are under the 

 influence of strong fleshy bundles, which firmly compress the orifices 

 when below water. Their sense of smell is well developed, and the 

 larynx simple. The brain in all is not only large, but far surpasses 

 in volume and in amount of convolutions that of the Land Carnivora 

 as a whole. Their docility and intelligence, especially when young, 

 are often remarkable. The voice is plaintive or bellowing, but want- 

 ing the great compass and strength of the Felidse. The nerves sup- 

 plying the organs of smell, sight, and hearing are large, and the last is 

 most unusually acute. Indeed, it is possibly to hearing more than to 

 the other senses that the Seal tribe are dependent for their safety and 

 living. The facts of sound readily travelling under water, of solid ice being also a good conductor, 

 and of the quietness of the frozen regions, all tend to render this faculty of the highest service, 

 nay, a necessity, to the creatures possessing it. Particularly is the faculty of hearing essential 

 when the Pinniped goes on land, for in the rarer medium of the air its vision is defective, the con- 

 struction of the lens, &c., being that best fitted for sight under water. 



TONGUE AND BACK PARTS OF MOUTH 



OF OTARIA. (Reduced after Murie.) 



to, Right Tonsil; w, Uvula, or Curtain; 



T, Tongue. 



