ARTICLE XII. 



Description of New Fresh Water and Land Shells. By Isaac Lea. Read 



Jan. 15, 1841. 



Lamarck, in describing the genus Melania, says that they are nearly all exotic. 

 In fact, he does not mention a single species as inhabiting the rivers of Europe. 

 In the United States, we find a great number distributed over a wide geogra- 

 phical range, from the Columbia River to the St. Lawrence. Separating Mr. 

 Say's genus Anculosa from Melania, we have remaining, described by him 

 and other Zoologists, about sixty species, which, with the fifty-seven now pro- 

 posed, will make the large number of about one hundred and seventeen species 

 known to inhabit the waters of the United States. The waters of Tennessee 

 seem particularly productive of the different forms of this genus, and I have no 

 doubt that many new ones will be added to the catalogue, as we have nume- 

 rous ardent and industrious naturalists labouring in the field of investigation. 



The greater part of the species which I now propose, it will be observed, 

 were collected by Dr. Troost, who, in his Geological Survey of the state of Ten- 

 nessee during several years, gave attention enough to its Natural History, to 

 enable us to add largely to the Mollusca already known. Mr. S. M. Edgar 

 and Dr. Currey, assistant geologists in that survey, have also obliged me by 

 the use of their specimens. 



As the indigenous and exotic species of the genus Melania now known are 

 so numerous, I propose to divide them into sections, comprising — 



1. The Smooth. 4. The Sulcate. 7. The Granulate. 



2. The Plicate. 5. The Striate. 8. The Cancellate. 



3. The Carinate. 6. The Tuberculate. 9. The Spinose. 



VIII. — 2 R 



