INTRODUCTION. (31 
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 
camiot be either accurate, or complete, and must be 
destitute of that full authority, which a thorough in- 
vestigation of all existing information on the same sub- 
ject alone can give. In this way the utility of the 
works of MM. Ferassac, Lamarck, and Deskayes 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 
established 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 mollusks of this country, and finding them to be 
unnoticed in the standard works of reference, have 
considered them to be unknown. 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 naturalists to describe 
them. They have therefore published the species, with 
as little apprehension of having been anticipated, as 
if they had been brought from the most remote and 
uncivilized countries. In this manner, well-known spe- 
vol. i. 17 
