NEW FRESH WATER AND LAND SHELLS.* 
Ir is now some years since I presented to this society a continuation of my discoveries 
of new forms from the fresh waters and soil of the United States. Since that period, 
owing to the kindness of many valued friends, I have been enabled to get together a much 
larger number by far, than could have been anticipated. ‘These have come chiefly from 
localities hitherto little examined, and which have produced new species more or less in- 
teresting. It will be observed that many are from Dr. Barratt, of Abbeville District, S.C., 
from Mr. Tuomey, of Alabama, Dr. Hale, of Alexandria, Louisiana, Prof. Powell, of Mem- 
phis, Major Le Conte, who procured them from Florida and Georgia, President Estabrook, 
of Knoxville, Tenn., Mr. Joseph Clark, of Cincinnati, Mr. C. M. Wheatley, of New York, 
and other kind friends. To them all, I return my sincere thanks for their liberality, and 
I trust that they will be induced not to flag in the cause of American science, but rather 
to be encouraged in the development of these new organic forms, which, in this branch 
of Zoology exist in such vast profusion, and in so extended a number of species, in the 
United States. 
Notwithstanding the vast number of well characterized species of the Family Unionide, 
(as there are also in the Family Melaniana,) there are continually new and distinct forms 
brought to our notice, which well deserve the attention of the American Zoologist. 
I am aware that many persons doubt the existence of so extended a production of 
species, but this arises from the want of a knowledge of them, closely cultivated and 
analytically examined. An organic form, instituted by nature must be recognised as dis- 
tinct, for it will remain in a state of autonomy to the end of its term. It is the duty of 
the zoologist to bring to the investigation an eye practised in discrimination, and a judg~ 
ment experienced in analysis, as well as also an honest intention of purpose, that he may 
give the best and most accurate results to his investigations. 
(* Read before the American Philosophical Society, March 5, 1852, and published in the ‘Transactions, 
Vol. X., New Series. ] 
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