ADVERTISEMENT. 
The six plates of American fresh-water Fishes herewith presented, like 
the plates of Astrangia Dane 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 Contributions of Knowledge, 
but are intended for distribution among those who will prize them on account 
of their historical associations. . 
8. P. LANGLEY, 
Secretary. 
SmrrHsonran INSTITUTION, 
Wasuinaton, D. C., March 22, 1889. 
