£4 INTRODUCTION. 
correct, condemns us to examine thoroughly all they 
have done ; and the more carelessness and haste their 
works exhibit, the more imperious in this respect is our 
duty. The unwelcome and growing burden of synon- 
ymy is thus imposed upon Natural History, there 
to remain, until it shall be cast off by some much 
needed reform in the artificial arrangements of the 
present system. Perhaps there is no branch of zoo- 
logy in which this evil has already become so un- 
manageable as in that of the testaceous mollusks ; 
and for this reason, we have thought that a few 
remarks on the subject, tending to explain the causes 
which have led to its existence, and pointing out 
the maimer hi which they may be avoided, might, 
in some degree, prevent its increase in this partic- 
ular department, and among the naturalists of the 
United States. 
We do not intend to discuss the cniestion, what con- 
stitutes a species ? for that would lead us too far from 
the end we propose ; but, in common with most natu- 
ralists, we shall take it for granted, that certain indi- 
viduals, possessing a common organization and simi- 
lar external characters, derived from a common and 
similarly endowed source, and propagating other indi- 
viduals identical in structure with themselves, do now 
exist, and -will continue to exhibit the same characters 
until they and their posterity become extinct. It is to 
these individuals, considered collectively, that we apply 
the name of species. Every species may be considered 
