Smithsonian Report. 19 39. —Meier 



PLATE 3 



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Courtesy of U. S. Public He.alth .Service. 



Diatoms Commonly Found in Water Supplies. 



1, Synedra pulchella with a solitary Pediastruin, an alca; 2, Synedra deHeatmima with alum floe. (Photo- 

 micrographs by Carl J. Lauter.) 3, Navkula; 4, Gomphnnema: 5, Asterionella. Greatly magnified. 



