FRESHWATER AND LAND SHELLS. 



Unio bengalensis. Plate II. fig. 3. 



Testa elUptica, transversa, incequilaterali, inflata ; valviilis tenuissimis ; natihus minute un- 

 dulalis; dentibus cardinalibus tenuibus el laminatis ; lateralibus sublongis, linearibusque ; 

 margarita purpured,. 



Shell elliptical, transverse, itiequilateral, inflated ; valves very thin ; beaks minutely 

 undulated ; cardinal teeth thin and lamellar; lateral teeth rather long and linear ; nacre 

 purple. 



Hab. Bengal. Dr Burroiigh. 



Cabinet of Dr Burrough. 

 Diam. -8, Length 1-3, Breadth 2-2 inches. 



Shell elliptical, transverse, inequilateral, inflated about the umbones ; 

 substance of the shell very thin ; beaks somewhat inflated, beautifully 

 and minutely undulated, the undulations being parallel and oblique to 

 the plane of the disk, and angular on the umbonial slope ; ligament 

 thin and straight; epidermis reddish brown and obscurely rayed; car- 

 dinal teeth very small, thin, lamellar, and single in both valves; lateral 

 teeth rather long, linear, slightly divided in the left valve ; anterior and 

 posterior cicatrices indistinct, and both confluent ; dorsal cicatrices 

 small, and placed in the centre of the cavity of the beaks ; palleal impres- 

 sion scarcely perceptible, and remote from the border ; cavity of the 

 shell deep ; cavity of the beaks rounded ; nacre very thin and purple. 



Remarks. — Among the numerous rare and beautiful shells brought 

 by Dr Burrough from his last voyage, was the single specimen descri- 

 bed above. It was purchased in Calcutta, and Dr B. thinks it inhabits 

 the Ganges. It is a very distinct species, and differs in the teeth from 

 all those with which I am acquainted. Without a close examina- 

 tion it might be taken for an Anodonta, the teeth being very small 

 and almost linear. In these it resembles somewhat the Symphynota 

 discoidea (nobis) and S. bi-alata (nobis), but the curve differs, and the 

 lateral tooth of the left valve is distinctly cleft. In the teeth there is 

 certainly a strong approximation to that group which possesses teeth 

 with a simple curve line. In the beaks it is remarkable for the close, 

 parallel undulations, which extend some distance from their apex, and 

 make, by being reflected, quite an acute angle on the umbonial slope. 



