INTRODUCTION. 



CHAPTER 1. 



GENERAL OBSERVATIONS. 



JL HE division or branch of natural history on which tliis 

 work treats, is called Conchology; it comprehends the 

 study and history of testaceous animals, and not only in- 

 cludes those of the sea, but also those of rivers and of tlit 

 land. 



Testaceous animals are such as have a calcareous co- 

 vering or habitation, in which the animal, otherwise na- 

 ked or fleshy, lives included and protected. 



All animals inhabiting shells are exsanguinous, and des- 

 titute of bones ; but they are endowed with a heart, Inngs, 

 mouth, and other organs adapted to their nature. 



It is perhaps necessary to prepare the young Concho- 

 logist with the knowledge, that all shells, in their various- 

 stages of growth, assume very diiferent appearances; in 

 the younger, the shell is usually fragile, thin, and semi- 

 transparent, and generally unprovided with the ribs, tu- 

 bercles, ramifications, and denticulations, which are ma- 

 nifest in those of maturer growth; the adults, however, as 

 they advance in age, become thick and ponderous; their 

 surface also becomes covered with callosities ; and they lose 

 that brilliancy of external colouring and marking which 

 had characterized their earlier state. But although these 

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