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Art. II. — New Urdonida oftht United States. 

 By Isaac Lea. 



In this paper I have continued the descriptions and observations on the indigenous 

 species which have come into my possession, since the last publication in the Society's 

 Journal. They are all from the States of Mississippi, Alabama, Georgia and North 

 Carolina, except a single one from Washington Territory. They consist of fifty- 

 three Uniones, four Margaritance, and one Anodonta. Many of them are of great in- 

 terest, and of forms which seem to be peculiar to those States. It is greatly to be 

 regretted that so few have been obtained with the soft parts, so important to the 

 development of our fresh water Mollusca. The illustrations will be found to be exe- 

 cuted with great accuracy and with a high finish. 



Unio insulsus. PI. 1, fig. 199. 



Testa ljevi, quadrata, inflata, insequilaterali, postice obtuse aDgulata, ad latere subplanulata ; valvulis sub- 

 crassis, natibus prominulis, ad apices rugoso-undulatis ; epidermide virido-fusca, insulse, striata, obso- 

 lete radiata ; dentibus cardinalibus parviuseulis, subeompressis, in utroque valvulo duplieibus; latcrali- 

 bus sublongis subcurvisque ; margarita vel alba vel purpurea et iridescente. . 



Shell smooth, quadrate, inflated, inequilateral, obtusely angular behind, flattened 

 at the sides ; valves rather thick, beaks somewhat prominent, rugosely undulate at 

 the tips ; epidermis greenish brown, dull, striate, obscurely radiate ; cardinal teeth 

 rather small, rather compressed, double in both valves; lateral teeth rather long and 

 somewhat curved; nacre white or purple and iridescent. 

 Tree. Acad. Nat, Sci. 1857, p. 86. 



Hah. — Roanoke River, Weldon, N. C. Prof. Emmons. 



My cabinet and cabinet of Prof. Emmons. 

 Diam. -7, Length IT, Breadth 1-9 inch. 



Shell smooth, quadrate, inflated, inequilateral, obtusely angular behind, slightly 

 flattened at the sides; substance of the shell rather thick ; beaks somewhat prominent; 

 rugosely undulate at the tips; ligament very short, rather thin and dark brown; 

 epidermis greenish brown, dull, obscurely rayed, striate below and witli distant 

 marks of growth ; umbonial slope raised, obtusely angular ; posterior slope rather 

 wide, slightly raised and obscurely rayed ; cardinal teeth rather small, somewhat 

 compressed, crenulate and double in both valves ; lateral teeth rather long and some- 



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