FLUVIATILE AND MADINE SHELLS 
OP 
NORTH AMERICA. 
[No. 1. The Article CoNCHOLoaY, from the third American edition of 
Nicholson’s Encyclopoedia, Philadelphia, 1819.*] 
We here introduce descriptions, illustrated by figures, of a few 
of the land and fresh water shells of the United States, induced 
particularly by the silence with which these productions of our 
country are regarded in the Systema Naturae. In the extensive 
work of Lister, entitled Historiae sive Synopsis Methodicae Con- 
chynorum,’^ &c., several of our shells are figured, and, to a few of 
them, short descriptions are annexed, not, however, designated with 
specific names ; of this work we have availed ourselves, from quo- 
tations and references. 
It will be readily perceived by the conchologist, that in the ar- 
rangement we have deviated from the course pursued in this work 
relative to the inviolability of the Linnaean system, so as to intro- 
duce some of the more recent improvements in the construction of 
genera, and that some considerable modifications are ventured to be 
made in this article. 
We think it proper to state, in addition to the above remarks, 
which were annexed to the descriptions in the first and second 
American editions of this work, that several species and three new 
genera are now added, which, with the exceptions of a small num- 
ber of new species now first published, we have previously given to 
the world, in several detached essays, in the pages of the Journal 
of the Academy of Natural Sciences, in the collection of which 
Academy all the specimens are preserved. 
*[The extracts are taken from the third edition. The previous editions 
are referred to in the Index. — En.] 
