INTRODUCTION. 7 



selves, that the best way is to select the shells which 

 have the animals alive in them; for those that are found 

 empty on the beach, are for the most part objectionable, 

 the shell becoming impaired by the co-operation of the 

 sun and waters, which also greatly tends to destroy the 

 beauty of the coloring and marking. 



Besides, a double advantage is to be derived from hav- 

 ing the animals alive, for, by keeping them in sea water, 

 much useful information may be obtained by an accurate 

 observation of their structure and habib. 



Storms frequently drive up live shells on the beach; 

 such should be collected as soon as possible, as they fre- 

 quently lose their delicate spines and foliations, by being 

 suffered to remain beating about on the shore. 



As land and river shells are seldom so beautifully 

 formed, marked, or colored, as those of the sea, they are 

 in consequence rarely so much prized; however, they 

 form an interesting part in all collections. 



The collector should always keep the following objects 

 in view, whenever he commences the arrangement of his 

 shells : 



First. The order to which they belong, that is, whe- 

 ther they are to class with the Multivalves, (i. e. shells 

 of many valves); Bivalves, (shells of two valves); or 

 Univalves, (shells of one part or piece only): which 

 three grand divisions constitute the leading distinctions 

 of shells. 



Secondly. He should be careful in placing them in 

 the proper genus of the order to which they belong. — 

 And, 



Thirdli/. He should avoid misplacing or confusing the 

 species which appertain to such genus; and if in the 



