BRITISH MAMMALS 



tidal rivers, whilst there are a few species among them 

 which can almost be regarded as fresh- water inhabitants. 

 The remarkable Narwhal, the male of which is the 

 possessor of an enormous spirally-twisted tusk in the 

 upper jaw, belongs to this family, but it is rarely seen off 

 the British Isles, as also is the Killer, or Grampus, which 

 is one of the largest and most ferocious of the Dolphin 

 family. The Cmomon Porpoise is the best known of all 

 the cetaceans which present themselves in our home 

 seas, and it is more frequently seen because it so often 

 comes close inshore, and will also ascend rivers. When 

 the animal is gambolling in the water, the triangular 

 large fin on the back is protruded above the surface. 

 The body is dark slate, or blackish, on the upper parts, 

 with pure white underneath. It is believed to feed 

 entirely upon fish, such as Mackerel, Herrings and 

 Pilchards ; but it is also accused of taking Salmon, 

 and probably ascends rivers for this purpose. It is of 

 social disposition, shoals or herds of considerable size 

 associating together, and when thus seen, their move- 

 ments cannot fail to excite all those who are interested 

 in the wild life of the mighty deep. 



Common Dolphin. — This, the last mammal with 

 which we are concerned (Fig. 26) is characterised by the 

 long beak, elongated back-fin and flippers, slender 

 body, small head, with a double array of sharp teeth 

 in the upper and lower jaws, running from forty to 

 sixty-five on each side. 



It is the best-known representative of the true Dolphins, 

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