INTRODUCTION. 



CHAPTER I. 



GENERAL OBSERVATIONS. 



THE division, or branch of natural history on wiiich this 

 work treats, is called Conchology; it comprehends the 

 study and history of testaceous animals, and not only 

 includes those of the sea, but also those of rivers and the 

 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 

 destiti\te of bones; but they are endowed with a heart, 

 lungs, mouth, and other organs adapted to their nature. 



It is perhaps necessary to prepare the young Coiicho- 

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

 ous stages of growth, assume very different appearances: 

 in the younger, the shell is usually fragile, thin, and se 

 mitransparent, and generally unprovided with the ribs, 

 tubercles, ramifications, and denticulations, which are- 

 manifest in those of maturer growth; the adults, howe- 

 ver, as they advance in age, become thick and ponder- 

 ous; their surface also is covered with callosities; and 



