ECONOMIC ZOOLOGY 499 



There are also a number of marine and fresh-water clams and 

 mussels which are used in smaller numbers. Some species of 

 gasteropods (snails) are prized in certain parts of the world. 

 It is believed that the mussels were an important article of food 

 to some tribes of North American Indians, and to some of the 

 peoples of the old world when they were in a corresponding stage 

 of development. Among the arthropods the lobster comes first 

 in importance, although it has been fished to such an extent that 

 the output is rapidly diminishing and the size of specimens is 

 steadily decreasing. Crayfish, shrimps, prawns, and crabs are 

 also used to some extent. The great class of insects furnishes 

 only the honey of the honey-bee. 



Every class of vertebrates furnishes food species. The 

 amphibians and the reptiles stand lowest in this respect. The 

 frogs and turtles and a few lizards are their only edible repre- 

 sentatives. The fishes, the birds, and the mammals furnish 

 the staple meat foods. A very large per cent, of the fishes are 

 recognized as edible. Many species of the sharks, even, are 

 prized although they are actively carnivorous, and the car- 

 nivorous animals have usually not been regarded as good to eat. 

 Many species of birds have been eaten, but those that rank as of 

 real importance belong chiefly to the Gallinae, the Columbae, and 

 the Anseres. These three orders of birds supply to man hun- 

 dreds of millions of dollars worth of his choicest food annually. 



Among the mammals many species have been eaten, but 

 the great division of ruminants and the swine furnish the 

 bulk of the meat food now used by the human race. The 

 horse is increasing in importance in this respect. Among 

 uncivilized people, before the domestication and improvement 

 of the ox, the sheep, and the hog, this division (ruminants) 

 still furnished the chief wild game animals. Besides meat they 

 furnish milk, butter, and cheese. In the far north the walrus, 

 the bear, and the reindeer take the place of these well-known 

 forms. 



502. Animals as a Source of Clothing for Man. In the 



case of primitive man the skins and furs of animals were the 

 sole source of clothing and one of the means of making tents 



