INTRODUCTION. vii 



through my hands, and to sucli an a- 

 mount as would appear incredible to any 

 one not interested in the science of Con- 

 chology. 



In this, as well as in every other branch 

 of natural history, the knowledge requi- 

 site to discover the scarce and rare vari- 

 eties from the common, can only be ac- 

 quired by practice. To particularize 

 objects that may present themselves to 

 the traveller, is not the aim of this work ; 

 but, for the benefit of science, and his 

 own interest, it is desirable to excite him 

 to collect all he may meet with, until he 

 has skill to select the good from the bad ; 



