SHELL 



5344 



SHELL 



SOME FORMS OF SHEI 



ical shell builders, and no other animal group 

 is so widely distributed. Their shells are found 

 not only along the ocean borders and in the 

 sands of the lake shores, but in low inland 

 plains, in swamps and even on high mountains. 

 These animals build their shells not as bees 

 make combs of wax; the fleshy covering of the 

 body, or mantle, secretes lime from the water, 

 and layer by layer the limy substance is added 

 to the growing shell. The latter is protected 

 from the corrosive action of acids in the water 

 by a horny, outer skin and a pearly lining. The 

 shells of mollusks are divided into two classes 

 the univalve, or those of one piece, and the 

 bivalve, those consisting of two parts joined by 

 a hinge. 



Of the first class, the graceful spiral or 

 wheel-like shells of the snails are most com- 

 mon, some being delicate, lustrous and pearly, 

 others, heavy, thick and dull. The single-piece 

 shells include also the rose-lipped covering of 

 the conch, a mollusk abundant on the Florida 

 coast; the cowrie shells which the child holds 

 to his ear to hear the sound of the sea; the 

 long, spindle shells of the warm waters of the 

 Pacific and the California shores; the hand- 

 some trumpet shells and giant whelks of the 



Atlantic; the tiny rice shells and the helmei 

 and cone shells of Southern United States. Th< 

 chambered nautilus of the deep seas, whicl 

 each year adds to its spiral shell a new cham 

 ber for which it forsakes the old one, is an 

 other interesting univalve mollusk. 



Clam and oyster shells are the most com- 

 mon bivalve shells, and the latter are also o: 

 great commercial importance because of theii 

 inner layer of pearl, called mother-of-pearl. 



Uses of Shells. Buttons, buckles, knife han 

 dies and many other articles are made fron 

 the pearly lining of the oyster shell, and a large 

 amount of white pearl is also obtained from th( 

 fresh-water mussels of the Mississippi River 

 especially between Quincy, 111., and Prairie di 

 Chien, Wis., and in the adjacent waters. Ovei 

 six billions of pearl buttons are annually manu- 

 factured in the United States. Mother-of-pear 

 is also extensively used for inlaying fane) 

 boxes, musical instruments, furniture and wal 

 panels, and as a covering for opera glasses, care 

 cases, etc. 



The beautiful greenish rnd rosy-hued aba- 

 lone shell, found in the California coast waters 

 is combined with the white pearl in inlay wori 

 and is also mounted in silver for jewelry 01 



