FRESHWATER AND LAND SHELLS. 41 



Unio Muhlfeldianus. Plate XII. fig. 36. 



Testa ellipticd, subcompressd, transversa, incequilaterali ; valvulis subcrassis; natibus sub- 

 prominulis, undulatis ; epidermide luleold radiata ; dentibus cardinalibus subparvis erectisque ; 

 lateralibus longis rectisque ; margarita alba et iridescente. 



Shell elliptical, rather compressed, transverse, inequilateral; valves rather thick; 

 beaks somewhat prominent, undulated ; epidermis yellowish, radiated ; cardinal teeth 

 rather small and erect ; lateral teeth long and straight ; nacre white and iridescent. 



Hab. Cumberland River, Ten. Professor Troost. 

 Cabinet of Professor Troost. 

 Diam. -8, Length l-S, Breadth 2-3 inches. 



Shell elliptical, rather compressed, transverse, inequilateral, rounded 

 before and behind, flattened on the umbonial slope; substance of the 

 shell rather thick before, thinner behind; beaks somewhat promi- 

 nent, with fine undulations at the tip ; ligament long ; epidermis yel- 

 lowish, with dark green rays on the posterior portion ; cardinal teeth 

 rather small, erect, and deeply cleft in the left valve ; lateral teeth 

 long and straight; anterior cicatrices distinct; posterior cicatrices con- 

 fluent ; dorsal cicatrices placed in the centre of the cavity of the beaks ; 

 cavity of the shell rather deep ; cavity of the beaks angular ; nacre 

 white and very iridescent behind. 



Hemarks. — The specimen before me was brought from the Cum- 

 berland River by Professor Troost, but I do not know from what part 

 of it. It seems to be more closely allied to U. iris (nobis) than any 

 species I have seen, but differs in being less transverse, more flattened 

 out behind, and in having the rays more distinct on the posterior por- 

 tion. I dedicate it to the distinguished custos of the Imperial Museum 

 at Vienna. 



A single valve closely resembling this species was sent to me some- 

 time since by my brother, T. G. Lea, from Cincinnati, but it is not 

 sufficiently perfect to decide on its being the same. 



VI. L 



