PORPOISES AND DOLPHINS 327 



should be noted for, of course, the two forms are quite unlike 

 one another, and placed in different families of the Toothed 

 Whales. In America the Bottle-nosed Dolphin is sometimes 

 referred to as the Common Porpoise, but it is preferable to 

 use the former name and to retain the other for Phncana 

 phoccena. 



The Bottle-nosed Dolphin is larger in size than any of the 

 " beaked " dolphins already dealt with, and is distinguished 

 by its short, well-defined snout 2 or 3 inches long. Placed in 

 the middle of the back is a prominent fin, the sharp apex of 

 which points backwards, so that the hinder margin of the fin is 

 concave. The flippers are moderate in size, tapering to a 

 point, with convex lower border and upper border convex 

 near the junction with the body and concave nearer the tip. 



The back is black or dark grey-brown and the belly is white. 

 The area on the under surface from vent to flukes is pigmented. 

 The head and snout are dark, but the upper lip edges and the 

 whole of the lower jaw are white, although the latter has 

 some mottling of pigment. Flippers and tail flukes are 

 pigmented. 



The number and size of the teeth help to distinguish this 

 species. Twenty to 22 pairs are visible on upper and lower 

 jaws, and the diameter of § inch is greater than in any of the 

 species of the preceding genus Lagenorhynchus, or of Delphinus, 

 the next genus to be described. 



The adult size is between 11 and 12 feet. Some of the large 

 specimens stranded on the British coast have shown signs of 

 advanced age in the form of diseased toothless gums and 

 arthritic backbones. 



The range of thjs dolphin is very wide. It is the commonest 

 species on the Atlantic coast of America, occurring from Maine 

 to Florida. It is found also in the Bay of Biscay in the 

 Mediterranean Sea, and has even been reported from New 

 Zealand. 



Its distribution in British waters, as indicated by stranded 

 specimens, is almost entirely confined to the west, south and 

 southern North Sea coasts. Sir Sidney Harmer pointed out 

 that its distribution is almost completely complementary to 

 that of the White-beaked Dolphin, the latter species having a 

 decided preference for the northern North Sea. 



