Two Mastogloia Thwaites ex W.Sm. taxa were found during a survey of the diatom flora of Lac de Guiers, Senegal. Based on all currently available literature, one taxon could be identified as M. belaensis M.Voigt, a species formerly described from Pakistan. The second species showed some resemblance to M. braunii Grunow. Analysis of the type of M. braunii revealed, however, important morphologic differences, leading to the description of a new species from the Senegal population: M. senegalensis Van de Vijver, Fofana, Sow & Ector sp. nov. The present paper describes this new species and discusses and illustrates the morphology of M. belaensis and the type of M. braunii. All taxa are discussed with morphologically similar taxa.
Bacillariophyceae, Mastogloia belaensis, Mastogloia braunii, new species, Senegal, ultrastructure.