How to Know Shells 



added; and when we think how changed is the attitude of scholars 

 toward sciences to-day, we may well marvel that so much has been 

 accomplished in so short a time. Science for its own sake is no 

 such real and vital thing as science in its relation to human life. 

 A great popular interest in natural sciences has followed the lead 

 of scientists. Generations of Nature-lovers are coming on. 



Conchology, as the name confesses, was the science of shells. 

 In 1800 two thousand species of shells were known. Now fifty 

 thousand species of mollusks are distinguished by name. The 

 whole specimen is studied to determine its relationships. Its life 

 history and habits are eagerly investigated. Thus has a dead 

 science come to life; and we shall see people opening their eyes 

 more and more to the wonderful forms of molluscan life that are 

 all about them, but which they have not yet learned how to see. 



The scope of the Mollusca is great. No other animal group 

 has so wide and varied a range of distribution. All latitudes 

 have their peculiar genera and species, excepting only the extreme 

 polar regions. Land shells range from tide water to snowy moun- 

 tain tops, to the limits of animal and vegetable life. Lakes and 

 rivers teem with fresh-water forms. Amphibious mollusks cluster 

 where land meets water. From the populous ocean border a 

 diminishing list of marine forms live on the ocean bed to abyssmal 

 depths. The pelagic mollusks live on the surface of the open sea. 



Mollusks there are that climb, leap, crawl, burrow, swim, 

 dive, float, even jly; for the graceful sea arrow which darts out 

 of water like a flying fish, is a squid, and squids are mollusks. 

 There is no mode of locomotion denied them. From microscopic 

 forms they range in size to the ponderous spindle-shell, a marine 

 snail two feet long, and the giant clam, four feet across, weighing 

 five hundred pounds. 



As scavengers on the ocean border and inland, mollusks are 

 important agents of sanitation, destroying disease germs in de- 

 caying organic matter, thereby purifying water and air. Snails 

 destroy noxious fungi and weeds. Mollusks furnish food to man 

 and other animals. To a large extent they are the food of cod and 

 other fish. Our dependence upon them is no less a fact because 

 it is indirect, as in this case. 



Oysters are preeminent among edible mollusks, with clams 

 and cockles, and snails and scallops in a long train after them. 

 An oyster is preeminent, too, as the source of the world's wealth 



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