64 INTRODUCTION. 



correct, condemns us to examine thoroughly all they 

 have done ; and the more carelessness and haste then* 

 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 moUusks ; 

 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 manner in 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 question, 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 



