Selected Sellaphora species from rivers and springs of the southeastern United States were studied by light (LM) and scanning electron (SEM) microscopy. Three new species are described here and two new combinations are made. Besides the traditional morphological characters, additional morphometric data were used to delineate species. Sellaphora hohnii is known only from Silver Springs, Florida, and S. rugula only from a tributary of the Savannah River, Georgia, while S. wallacei and S. meridionalis have wider distributions, but are currently known only from the Southeastern U.S. S. rexii is apparently a globally distributed species. All five species usually have low relative abundances in river samples.