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Art. IX. — Descriptions of the Soft Paris of one hundred and forty-three species and 

 some Embryonic Forms of Unionidce of the United States. 



By Isaac Lea. 



Until within a recent date, comparatively few writers on Conchology had given 

 attention to the soft parts of the animals included in the shell, — the outward 

 enveloping parts. Poli, Cuvier, Lamarck, Cams, Moquin-Tandon, and a few others, 

 taught the importance of making diagnoses of such species as could be procured, 

 and thus more natural classifications have been made. Having, about thirty-five 

 years since, observed in our Unionidce structural differences of the branchial uterus 

 — then called oviducts — I carefully described and figured in my first paper on our 

 Fresh-Water Mollusca, (Trans. Amer. Phil. Soc, Nov., 1827,) the singular and 

 interesting structure of the Unio irroratus, then first described. And, in the same 

 paper, I stated the uses, in this family, of some of the muscles and the vast repro- 

 ductive capability of some of the species. Subsequently, in the same Transactions, 

 1836, I described the forms of the branchial uterus of five species and gave correct, 

 representations of them, (see vol. vi. pi. 15). About eight years since, I entered 

 into the examination of a large number of species, kindly sent to me by various 

 friends from different States, in a living condition or in alcohol. Some of them 

 have been published in the Journ. of the Acad, of Nat. Sci., in 1858 and subsequent 

 years. In that year I also published diagnoses and figures of the forms of the 

 embryonic shell of thirty-eight species. It is not my intention here to redescribe 

 the outward or hard parts — the exoskeleton — of those species which have been 

 described, but simply the included soft parts of such as have come into my posses- 

 sion and have not heretofore been given. The labor has been very great, for in 

 some cases fifty to one hundred specimens of a species have been carefully exa- 

 mined before the diagnosis was made. As most of the specimens were in alcohol, 

 allowance must be made for difference in color, shrinkage, as well also for difference 

 of age, as sometimes only a few or a single one was in my possession. In my vols. 

 i., ii., vi., vii., viii. and ix.. taken from the Trans. Amer. Phil. Soc. and the Journal 



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