The study of diatom taxonomy most frequently uses light microscopy to distinguish the silicous cell wall components of different species. The structures that give a characteristic appearance in the light microscope are usually patterns that reflect the ultrastructure of the cell wall that cannot be resolved adequately with this technique. Scanning electron microscopy provides a more complete concept of diatom valve structure, especially for diatoms that are less than 10 um in length. While examining a collection of epipelic diatoms from Lake Kathrine, Michigan, during 1979 and 1980, a number of small Fragilariaceae were encountered which could not be easily identified with the light microscope.