14 INTRODUCTION. 



The serpulae, balani, chamae, and anomiae, often affix 

 themselves in clusters to the shells of other genera; and al- 

 though they destroy the beauty and symmetry of the shell, 

 they very rarely injure its inhabitant. 



Shell-fish, though they in part constitute the food of 

 animals, birds, and fish, yet, in their turn, have some op- 

 portunity of retaliation, by partially destroying the float- 

 ing habitation of the universal despoiler, Man ; the Pho- 

 las arid Teredo navalis, in particular, frequently commit 

 such serious injury on ships, by boring into their planks, 

 as often to endanger the safety of the vessel, if not speed- 

 ily prevented in their operations. 



DIRECTIONS FOR COLLECTING SHELLS, AND ARRANGING THEM 

 SYSTEMATICALLY. 



WITH regard to collecting shells, it is necessary to hint 

 to those students, who, by a residence on the sea coast, 

 may have an opportunity of forming collections for them- 

 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 colouring 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 habits. 



Storms frequently drive up live shells on the beach: 

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



