6 



POPULAR CONCHOLOGY. 



have a stream of water continually presented to 

 them, and in those which live in air, of organs 

 fit for its respiration. 



Mollusca are to be found in all parts of the 

 world, in the sea, in rivers, and on land, and 

 differ in their construction and habits according 

 to their locality. A great number have their 

 residence in the sea, and are unable to exist 

 out of salt water ; of these some float on the 

 surface, others have the power of moving 

 through the deep waters, and others again are 

 attached by various means to rocks and other 

 substances below the surface. Many species 

 are met with, living on the sea coast, in the 

 sand, mud, or cliffs, and many in rivers : the 

 land also has its peculiar varieties, either 

 living under ground, in holes of trees, or in 

 moist and marshy places. These different ha- 

 bitations give a general name to the Mollusca 

 which are found in them, as Pelagic*, to those 

 which reside in the deep recesses of the ocean, 

 Litoral^ to such as are found on the coast, 



* From pelagus, Lat., the depth of the sea, 

 f From Uteris, Lat., of the shore. 



