DOLPHINS 239 



and defines no less than fifty.* Many of these names 

 will, however, ultimately have to be weeded out from 

 the lists which they encumber. Everyone nowadays 

 will agree with Sir William Flower when he observes 



O 



that it is necessary to abandon "the old assumption, 

 upon which so many new species were founded, which 

 limited the area of each species to a small and circum- 

 scribed portion of the ocean, and placed imaginary 

 barriers to its distribution where none really existed." 

 It is this perversity which has confounded the whole 

 history of whales, and especially of that family which 

 is now under consideration. Like other animals, too, 

 the Dolphins show some alterations in structure as 

 they pass from immaturity to old age. And these 

 alterations have to be taken very careful account of, as 

 they relate to features which have been made use of 

 for specific, and even generic, definition by Dr. Gray 

 and others. A number of these anatomical points are 

 brought together by Sir W. Flower in his essay f 

 upon the generic subdivisions of the Dolphins. In 

 the first place the length and width of the beak alters 

 with advancing years, and it becomes longer and 

 wider in proportion to the rest of the skull in 

 perfectly adult animals. 



Another character which is commonly made use of 

 in the discrimination of species is the number and 



* There is no doubt that there are at least some thirty to thirty-five 

 species on the lowest estimate. In view of the scattered and imperfect 

 character of much of the literature relating to this family, the reader will 

 have to regard the list of known forms as only approximately true. 



t " On the Characters and Divisions of the Family Delphinidae," 

 Proc. Zool. Sac., 1883, p. 466. 



