DOLPHINS 241 



the possibility of accurately dividing up the family, a 

 considerable number of definite types can be recog- 

 nised, which may fairly be termed generic. To go 

 further than this is not so easy. The most recent 

 arrangement of the dolphins is that of Mr. True,* 

 who attempts to distinguish the species into which the 

 genera allowed by Sir W. Flower can be divided. 



The admitted genera of dolphins are some nineteen. 

 These will be allowed here. Seeing that there are 

 so many types to which generic rank should perhaps 

 be allowed, it becomes a matter of importance to 

 inquire how far they can be grouped together ; 

 whether in fact any practical subdivision of the family 

 into larger divisions than genera can be arrived at. 

 Several authors are in favour of separating the Beluga 

 and the Narwhal of the north into such a sub-family; 

 there is no doubt that in more than one character 

 these two northern forms approach each other to differ 

 from the remaining forms, f The cervical vertebrae 

 are never fused, even in perfectly adult animals, with- 

 out epiphyses to the vertebrae ; in other dolphins 

 more or fewer are fused. The pterygoid bones are 

 somewhat rudimentary, not having the involuted 

 cavity below, which is a character of other dolphins ; 

 these two bones, moreover, are not merely widely 

 separated, which is found in other dolphins, but are 

 bent towards each other posteriorly, and also articulate 



* Bull. U.S. Nat. Mus., 1889. 



t It is highly interesting to note in this connection that, according to 

 van Beneden, the natives of Greenland and the Esquimaux regard the 

 Beluga as the female of the Narwhal. 



