

ARTICLE IV. 



Description of New Fresh Water and Land Shells. By Isaac Lea. Read May 2d, 1845. 



The rich Fauna of our country, not yet completely explored, gives me the opportunity 

 of again presenting myself before the Society with descriptions of many new organisms of 

 an interesting nature to the zoologist. The unexplored portions of Tennessee, Alabama, 

 and Louisiana contribute nearly the -whole of the species composing this paper — some of 

 them of more than ordinary interest. It will be observed that I have now added twenty- 

 three new species to the already long list of the Melanise, my last paper containing fifty- 

 seven. I also add six to the interesting genus Sckizostoma — now making ten species in 

 all — and twenty-six to the family Naiades. 



In the investigation and necessary research to make myself acquainted with the genus 

 Melanin. I have necessarily looked up the names of all the known species, and for my own 

 convenience have made an alphabetic list, which I propose to append, for the convenience 

 of those -who study this genus. The whole consists of three hundred and ninety-five 

 name-, by various authors, but I do not mean to be understood that these; are all distinct 

 species — a few are doubtless duplicated. Pari of them are fossil. 



Regarding my own species, it will be observed that, among some of them, there is a 

 strong alliance; but I have abstained from considering them as typical where 1 could not 

 find what I presumed to be a constant character. At the same time, I am perfectly 

 aware of the extreme difficulty of separation, arising from the fact of the existence of the 

 vasl number of specie- now described as belonging to this genus, and their consequent 

 inosculation. Where my mind was satisfied, however, alter a close and careful exami- 

 nation, that their characteristics were persistent, I have put them down with confidence 

 that they would, in the main, be found to be correct. 



I Mo mi PI. I. Fig. 1. 



Train plicatd, elliptic^, valde in/Iii/n: valoulit subcrassis; natibus prominulis; epidermide luleo-Jiucd, 

 ttriatdj denlibui cardinalibus subgrandibus ; laU parvit curvisque; margarild albd <t iridescenle. 



Shell elliptical, folded, much inflated; valves rather thick; beaks rather prominent; epidermis yellowish-brOWDi 

 striate; cardinal teeth rather large; lateral teeth small and curved; nacre while and iridescent. 



