6 PREFACE. 



The genera Orca and Orcella are uot touched upon in tbis paper. 

 Tbe species of the latter genus ueed uo elucidation. In the case of 

 Orca, tlie material which I gathered is scanty, and I abstain from dis 

 cussing it for fear of adding to, rather than lessening, tbe confusion in 

 which the genus is involved. Many additional facts must be obtained 

 before even a tolerably satisfactory account of the killers can be written. 



In conclusion it is necessary that I should say a few words regarding 

 Professor Flower's paper "On the Characters and Divisions of the 

 Family Delphinida; " (Proc. Zool. Soc. Loudon, 1883). As I have already 

 stated, tbe proof-sheets of this valuable essay were very kindly placed 

 in my hands by the author at the outset of my studies, and I have un- 

 doubtedly becu influenced, to a great extent, by the opinions therein 

 expressed. The grounds covered by this essay and my own, however, 

 are somewbat different. Regarding his work, Professor Flower writes : 



It is, however, not so much to specific distiuctions that this research has been 

 directed, as to discover the mutual relations of the different modifications of tlic Dol- 

 phin type to one another, and their association into groups which may be considered 

 (following the custom adopted in the arrangement of other groups)of generic value.* 



My own work, on the contrary, has been directed not at all toward 

 the distinction of genera, but rather toward the determination of species. 



I have accepted the generic divisions employed by Professor Flower 

 for the most part without alteration, as the basis of my work. 



* Flower: Proc. Zool. Soc. Loudon, 1883, p. 469, 



