2 INTRODUCTION. 



ternal coloring and marking which had characterized 

 their earher periods. But although these differences, in 

 some instances, are sufficient to excite a considerable de- 

 gree of perplexity, yet there is always a certain appear- 

 ance by which the Conchologist will be able to distinguish 

 the genus and species by the shells alone ; for every genus 

 and species have their generic and specific characters, 

 either in color, work, or substance, which the shells of 

 that genus almost invariably retain in all their stages of 

 growth and varieties of form, and consequently are thereby 

 easily known and distinguished. 



Properties of Animals inhabiting Shells, 

 These animals possess the power of extending or aggran- 

 dizing their calcareous habitation or shell, and are also 

 enabled to repair whatever breaches this brittle dwelling 

 may have sustained, by the turbulence of the tempestu- 

 ous ocean. The operation of enlarging and repairing 

 the shell is supposed to be effected by a peculiar en- 

 dowment of the animal, which can at pleasure discharge 

 a viscous humor, and which readily becomes hardened 

 or consolidated, and soon acquires the consistence of the 

 rest of the shell. 



Many shells are covered with a cutaneous or skin-like 

 substance, called the epidermis, which serves to protect 

 the beautiful colors and workings which are frequently 

 concealed beneath it. 



Customaryiises to which Shells and their Inhalitants 



are converted. 



The principal benefit derived by man from shell-fish, 



appears to be in the way of food. Whole countries are 



known to have no other sustenance for weeks together 



p^^' • v.- 

 ?j " ■ ■ 1 



