INTRODUCTION. 



CONCHOLOGY is a science which embraces the know- 

 ledg-e, arrangement, and description of testaceous bodies, 

 and which, according- to the system of Linnaeus, 

 adopted in this Treatise, has for its basis the exter- 

 nal form and character of the shell, and is totally in- 

 dependent of the animal enclosed within the calcareous 

 covering. 



The animal is a soft, fleshy, exsanguinous substance, 

 without bones, but generally furnished exteriorly with 

 a muscle, by which it adheres to the shell, occasioning 

 certain indentations, thence called muscular impres- 

 sions. Like other animals, it is endued with lungs, heart, 

 mouth, and organs peculiarly adapted to its nature. 



The inhabitants of Multivalves and Bivalves are vi- 

 viparous, but of Univalves some are oviparous. It ap- 

 pears from the investigations of Leuwenhoeck on Bi- 

 valves, and of Reaumur on Univalves, that the animal 

 is furnished with a shell before it leaves the parent or 

 the egg; and as it subsequently increases in magni- 

 tude, the part which is protruded beyond the origi- 

 nal limits of the shell becomes covered with a viscous 

 matter, which on desiccation forms a thin and elas- 

 tic substance, in addition to the previous formation. 



