A new diatom species, Mayamaea cahabaensis, was observed during analysis of algal samples collected from Alabama (USA) by the U.S. Geological Survey's National Water Quality Assessment Program (NAWQA). Subsequently, other populations of the same species were found in material collected for a United States Environmental Protection Agency (EPA) project also from Alabama streams. A review of NAWQA materials at the Academy of Natural Sciences of Philadelphia (ANSP) revealed that the species was also found in Arkansas, Arizona and Texas. Light microscopy (LM) and scanning electron microscopy (SEM) features reveal an affinity of the new taxon with Mayamaea Lange-Bertalot. Some of these features include elliptical valves with rounded ends and parallel to radiate striae composed of round areolae, which are occluded by a hymen positioned toward the external opening of each individual areola. The valves are slightly asymmetrical about the median transapical plane. The asymmetry of the valves and the clarity of the valve ornamentations under LM are features that are not seen in other members of the genus. The new species is eutraphentic and was found in warm waters with medium conductivity. So far, only freshwater stream populations have been found with no records from lakes.
New taxa: Mayamaea cahabaensis Morales and Manoylov