INTRODUCTION. 



61 



those named, -without having the means of knowing 

 what progress has been made in the science in every 

 country, is but ill prepared for his task. His work 

 cannot be either accurate, or complete, and must be 

 destitute of that full authority, which a thorough in- 

 vestigation of aU existing information on the same sub- 

 ject alone can give. In this way the utility of the 

 works of MM. Ferussac, Lamarck, and Deshayes is 

 very much impaired ; all of them being exceedingly 

 incomplete and unsatisfactory in American species. 



Besides the species which were published by Mr. 

 Say at the distant period before mentioned, numerous 

 others have, in the interval of twenty years, been 

 estabhshed by him and other American authors, very 

 few of which, it is believed, have found a place in any 

 foreign systematic work. The result of this omission 

 has been what might be expected ; insulated natural- 

 ists in various parts of Europe, obtaining from time to 

 time, through travellers and friends, some of the com- 

 mon moUusks of this country, and finding them to be 

 unnoticed in the standard works of reference, have 

 considered them to be miknoAni. It seems never to 

 have occurred to them, that these shells might have 

 been described on the spot where they exist, or, in- 

 deed, that there could be native naturahsts to describe 

 them. They have therefore pubhshed the species, with 

 as httle apprehension of having been anticipated, as 

 if they had been brought from the most remote and 

 uncivilized countries. In this manner, well-kno-wii spe- 



