26 LIVING CREATURES. 



will say, when you remember that when a hard piece 

 of leather or a rough temper is softened, it is said to 

 be mollified. 



Something further must be observed. The shells 

 of the fresh-water clam, the salt-water clam, and the 

 oyster open like a book with a hinge at its back. 

 Break the hinge and there are two shells nearly alike. 

 The snail shell can not be opened in this way. It is 

 single, and looks as if it had been whirled or twisted. 



It is plain that, besides protecting them against vio- 

 lence, these shells are designed in part to shut the 

 water out and to shut the soft animals, or mol- 

 lusks, in. Opening and closing perfectly light, they 

 act like the valves of a pump. They are, there- 

 fore, called valves. The clam, mussel, and oyster, 

 having two shells, are called bi-valves. The snail 

 and its kin, having but one shell, are called uni-valves. 

 There is a long list of shell animals that are clam-like, 

 and a long and brilliant one that are snail-like. 



5. THE CLAM. 



ABOUT the year 1626, John Smith, the founder of 

 Virginia and the author of the charming story of 

 Pocahontas, wrote a book about his adopted country. 

 In this book he describes the natural attractions of 

 Virginia ; and among other good things, he mentions 

 the mollusk which is the subject of this chapter. 

 "You shall scarce find," says he, ''any bay or shallow 



