'"PH ROUGH the kindness, and liberality, of Professor Joseph 

 Henry, Secretary of the Smithsonian Institution, we have 

 been permitted to take electrotype copies of numerous wood-cuts, 

 originally prepared for its own publications.* In this way, we 

 have been enabled, fully to illustrate the present work an ad- 

 vantage which would, otherwise, have been unattainable, on 

 account of the cost. 



* The figures of Unionida were drawn from nature, and cut especially for the present 

 purpose. 



M90583 



