PORPOISES AND KILLERS. 63 



in the chapter on " Tusks." Allied to the narwhal is the 

 beautiful white-whale (Beluga), which is likewise a 

 northern species, distinguished by its glistening white 

 skin, the absence of any tusk, and the presence of 

 numerous well -developed teeth in the fore part of the 

 jaws ; neither of these species having a back-fin. 



Although the name "porpoise "is applied indiscriminately 

 to several members of the family, it should properly be 

 restricted to a few comparatively small-sized species 

 characterized by the presence of some twenty-five small 

 and flattened teeth with spade- shaped crowns on either 

 side of each jaw. Porpoises are among the most common 

 and familiar of all cetaceans, their rolling gambols being 

 well known to all who have made a voyage ; but 

 whereas the common porpoise has a distinct back- 

 fin, in the species represented in our illustration that 

 appendage is lacking. Less familiar, on the other 

 hand, are the much larger and handsomely coloured 

 killers, or grampuses (Oreo), differing by the great size 

 of their teeth (Fig. 21), which are usually twelve in number 

 on each side, and the great development of the back-fin. 



FIG. 23. Pacific Black-Fisli. (From True, Bull. U. S. Nat. If us.) 



Attaining a length of about twenty-five feet, the killer 

 derives its title from its rapacious habits ; a single specimen 

 having been known to swallow several whole seals in 

 succession, while not unfrequently several individuals have 

 been observed to combine their forces to attack and kill the 

 larger members of the order. Killers may always be 

 easily recognized while swimming near the surface by the 



