276 



ECONOMIC ZOOLOGY 



As a matter of convenience the single order, Cetacea, will be used 

 here, and one or two members of each of the above two groups will 

 be discussed from the economic standpoint. 



The whales are wholly aquatic in habits and hence are fish-like in 

 form. The anterior appendages are developed into flippers, the pos- 



PiG. 179. Skull of Greenland whale, Balaena mysticetus, showing whalebone. 

 X;H$o- (From Hegner, College Zoology, after Sedgwick, from regne animal.) 



terior appendages are usually entirely wanting and the pelvic girdle 

 is vestigial. The tail is flattened vertically and is divided into right 

 and left flukes, and by its vigorous up-and-down motion propels the 

 animal with the speed of a steamship. The body is practically devoid 

 of hair and is surrounded, beneath the skin, by a layer of fat (blubber) 



PIG. 1 80. The dolphin, Delphinus del-phis. xKo- (From Hegner, College 

 Zoology, after Sedgwick, from regne animal.) 



that serves to keep the animal warm in the cold water in which it 

 usually lives. The nostrils are in the form of spiracles on top of 

 the head, from which a jet of moist breath causes the appearance of 

 "spouting." The eyes are very small and no external ears are present. 

 In the toothed whales numerous teeth are present in the adults, in the 

 whalebone whales teeth are present only in the embryos, the adults 



