1226 THE CETACEANS 



harassing and attacking the whale, were killers, I have no reasonabe doubt, but 

 the question arises as to the nature of the animal to which the strange white tail- 

 like object seen standing above the water could have belonged. My impression at 

 the time was that it must be the upper lobe of the tail of some enormous shark 

 allied to the threshers {Alopecias}, and this impression has been confirmed by a 

 subsequent examination of the stuffed specimens of that genus in the British Mu- 

 seum. The thresher is, however, a black shark; while the minute size of its teeth 

 seems to discredit the common accounts of its attacking whales. Unless, however, 

 it could have been the flipper of a humpback, I am at a loss to imagine to what other 

 animal the aforesaid white tail-like object could have belonged, save to some 

 gigantic shark allied to the thresher, but of a white color, and probably armed with 

 much larger teeth. 



THE LESSER KILLER 

 Genus Pseudorca 



An adventitious interest attaches to the Cetacean known as the lesser killer 

 {Pseudorca crassidens) owing to its having been originally described on the evidence 

 of a skull dug up in the Lincolnshire fens, which was for a long time regarded as 

 pertaining to an extinct species. This animal is distinguished from the killer by its 

 smaller back fin, the pointed flippers, and the cylindrical roots of the teeth, as 

 well as by certain features in the structure of the skull. In color the lesser killer 

 is entirely black, and it attains a length of about fourteen feet. There are gen- 

 erally eight teeth in the upper jaw on each side, and ten in the lower jaw. This 

 species appears to be cosmopolitan, having been met with in small herds on the 

 coast of Denmark, and also in Tasmania. Its habits are probably somewhat similar 

 to those of the killer. 



THE BLACKFISH 

 Genus Globiocephalus 



The blackfish (Globiocephalus melas] derives its English name from its nearly 

 uniform black coloration, while its generic title refers to the characteristic globular 

 form of the head. In size this species is one of the largest representatives of the 

 family, attaining a length of about twenty feet. 



In addition to its beakless globular head, the blackfish is characterized by the 

 long, low, and thick back fin, the long and narrow flippers, and the small size and 

 number of the teeth, which are confined to the front of the jaws. The usual num- 

 ber of the teeth is from eight to twelve on each side of the jaws, but in a distinct 

 variety or species from the Bay of Bengal they are rather fewer. The skull is very 

 broad and much depressed, and the union between the two branches of the lower 

 jaw very short. In the typical form there is a large spear-shaped white area on 

 the chest, extending from the corners of the mouth to the flippers. This white 

 area, is, however, absent in certain forms, which have been regarded as indicating 

 distinct species. 



