438 DELPHINID^. 



the upper one slightly overhangs the lower ; the blow- 

 hole is just above the eyes. The anterior part of the 

 body is nearly cylindrical, the remaining portion to the 

 tail conical ; in this latter region there are low ridges 

 on the back and belly, and less distinctly marked lateral 

 ridges, giving a sub-quadrangular form to the posterior 

 part of the body. There is no dorsal fin, and the flippers 

 are very small. The upper parts are dusky or blackish 

 grey, varied with marblings and spots of a darker shade, 

 the lower parts are white, marked on the flanks with 

 numerous grey or black spots. The young are bluish 

 grey, and the animal appears to become lighter in colour 

 with age. 



The great projecting tusk or " horn " which is so charac- 

 teristic of the Narwhal, is the left canine tooth, which is 

 developed to this enormous size, while its companion 

 remains abortive ; it is produced from the maxillary bone 

 and not from the intermaxillary, as was believed by 

 Cuvier. In the young animal, and usually in the adult 

 female, the rudimentary canines lie parallel to one 

 another in the hollowed- out maxillaries, and consequently 

 when the left tooth is developed it grows straight forward 

 and forms an immense tusk or spear, projecting from the 

 animal's snout in the direct line of the body. This tusk 

 in the adult reaches a length of six or eight feet, or even 

 more, and is covered with spiral markings, twisting from 

 right to left ; the point is somewhat blunt and the anterior 

 portion is usually smooth and polished. As already 

 mentioned, the tusk is seldom developed in the female, 

 but several instances are on record in which it has 

 assumed a considerable size. 



Occasionally, though but rarely, both tusks are 

 developed. This is well exemplified in a very fine 

 Greenland skeleton, which we had recently the jjleasure 



