ADVERTISEMENT. 



The six plates of American fresh-water Fishes herewith presented, like 

 the plates of Astrangia Daiiw recently issued by the Smithsonian Institution, 

 are published, not primarily on account of any new knowledge which they are 

 supposed to convey, but as a memorial of a project undertaken early in the 

 history of American science, by two of the most eminent naturalists this coun- 

 try has ever possessed. 



They will not be included in the series of Contributinns of Knowledge, 

 but are intended for distribution among those who will prize them on account 

 of their historical associations. 



S. P. LANGLEY, 



Secre/a}y, 



Smithsonian Institution, 



^yAS^INUTON, D. C, March 22, 1889. 



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