TO 



WILLIAM HEMBEL, ESQUIRE, 



ONE OF THE VICE PRESIDENTS OF THE ACADEMY OF NATURAL 

 SCIENCES OF PHILADELPHIA, &C. 



DEAR SIR, 



In publicly addressing to your notice a trans- 

 lation of Prof. RAFINESQUE'S Monograph of the 

 bivalve shells of the river Ohio and its -tributa- 

 ries, it seems proper to remark, that this paper 

 was originally published at Brussels, in Septem- 

 ber, 1820, in " les Annales generales des Sciences 

 physiques." Extra copies were transmitted to 

 the author in this country, who distributed them 

 among individuals, and the libraries belonging to 



M94104 



