102 UNIVALVES. 



its spoil. When taken, the janthina emits about a tea- 

 spoonful of a deep purple fluid, in order, perhaps, like 

 the cuttle-fish, to darken the water around, and thus 

 elude the pursuit of his enemies. 



Shells have long excited interest. In many a humble 

 dwelling they may be seen ; while, in habitations of a 

 higher order they often appear as the result of a choice 

 directed by intelligence and taste. Many a specimen, 

 too, is associated with the remembrance of a delightful 

 search on the sands when the tide was out ; of inter- 

 course which gladdens and improves the heart ; and 

 of scenes which have left impressions on the mind not 

 to be effaced. What interesting materials for conver- 

 sation might be found, were an acquaintance with their 

 circumstances more general ! 



The shells of the mollusca are formed either of one 

 piece, or of several ; the separate pieces, in either case, 

 being termed valves : so that shells may be univalve 

 when they consist of one, bivalve of two, and multi- 

 valve of a great number of pieces. 



The univalves are the most simple. They have two 

 principal parts : one of which is distended, called the 

 body, and the other tapering, called the spire, as in the 

 engraving on p. 103. The latter is formed by the parts 

 which roll round, and are called whorls, from an old 



