1 .\T KOI) rCT 1 ON. 



Sinco the issuing of my last volume (7th), many now species of the Unioniilie have come into 

 my possession, and I now give full descriptions and remarks upon most of them. The Southern 

 States, and particularly Alabama, Mississippi, Georgia and North Carolina, have multiplied them 

 greatly. The very remarkable diffusion of species of this kind of Zoological life in so many 

 varied forms, some of thorn so nearly allied, will strike the attention of the student, for no other 

 portion of the globe exhibits anj'thing at all kindred to this remarkable development. Many 

 friends in these States have, with untiring industry, contributed to the collection and examina- 

 tion of the Molluscs of their magnificent and numerous rivers, small streams and pools; and it 

 may be said, without fear of contradiction, that, notwithstanding such rich harvests have been 

 reaped, that very much remains to be gleaned from numerous habitats which have not had the 

 eye of the Naturalist to peer into their resources. Nature has been so lavish in these States, 

 that, although the greater and smaller streams permeate in every direction, still nearly all seem 

 to have some peculiar form pertaining to each. Unfortunately the existing troubles in the South 

 have cut off these investigations, and until peace shall return to open again scientific correspond- 

 ence, the prosecution of these researches will naturally remain interrupted. 



In the introduction to my last volume I enumerated the species of the Family rnioniiliE 

 described to that time as inhabiting the United States. 



The number was then in the United States, 550 ; in other parts of North America, .38. 



Up to this time we have in the United States, 607 ; which are thus divided : 

 Unio, .... 520 

 Margaritana, ... 28 



Anodonta, ... .59 



607 



To those may be added for the remaining part of North America, 39 species; making together 

 646 species of the Farailj' now known. 



Judging from the constant flow, for a few 5''ears back, of new species from many obliging 

 friends in the South, I cannot doubt but that a large number will still be found. 



Texas has yet been but very slightly examined, and its branching streams, watering the soil in 

 every direction, must be productive of riches in these molluscs, which will fully reward the labor 

 of the Naturalist. A large portion of Louisiana, Mississippi and Alabama has not been examined, 

 and Florida is almost a virgin field for investigation. 



It will be observed that this volume is confined to American species. In the next volume I 

 propose to issue in part the descriptions and figures of Exotic species, the manuscript of which 

 is now ready, and the plates oxocutod on stone. Those are chiefly from South America, and wore 

 collected by ray friend. Prof. Jeffries Wyman, during his late scientific voyage. The simple diag- 

 noses of these have already appeared in the Proceedings of the Academy of Natural Sciences. 

 In this volume there are 104 species described and figured, and the names of those friends who 

 huvo kiiully sent thorn to iiic will bo found to bo attai-hed U> oncli doscription. 



