278 ECONOMIC ZOOLOGY 



whale is the Greenland, an Arctic form yielding valuable oil and whale 

 bone. 



The finbacks, Fig. 183, and humpbacks, Fig. 184, are the forms 

 most commonly killed at present. 



PIG. 183. Common finback whale, Balaenoptera physalus. (After Rabot, Whale 

 Fisheries of the World.) 



The killer whale, Orca orca, is a voracious form, 20 feet or more in 

 length, that is very destructive attacking all marine animals, even the 

 largest whales. 



The narwhale, Monodon monoceras, is an Arctic form, one of whose 

 upper teeth is prolonged into a twisted horizontal tusk 5 or 6 feet in 

 length. 



FIG. 184. North American humpback whale, Megaptera nodosa. (After Rabot, 

 Whale Fisheries of the World.) 



There are numerous other species that more or less closely resemble 

 those mentioned above. 



One of the first and most important of the uses to which whales have 

 been put is the production of sperm oil. Oil has been used for illumi- 

 nation and other purposes for ages, probably since the seventh century. 



