INTRODUCTION. 
CONCHOLOGY isa science which embraces the know- 
ledge, arrangement, and description of testaceous bodies, 
and which, according to the system of Linneus, 
adopted in this Treatise, has for its basis the exter- 
nal form and character of the shell, and is totally m- 
dependent of the animal enclosed within the calcareous 
covering. 
The animal is a soft, fleshy, exsanguinous substance, 
without bones, but generally furnished exteriorly with 
amuscle, 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, 
