We present light and scanning electron microscopy on two new species of Prestauroneis from the Zoigê Wetland,Sichuan Province,China.Prestauroneis nenwai sp.nov.is rhomboid in shape with acutely-rounded apices.Striae around the central area are more widely spaced than elsewhere on the valve,and distinct pseudosepta are present.This new species is distinguished from the two previously described species in this genus by the shape and size of the valves.Prestauroneis lowei sp.nov.is more elliptical in outline,with barely protracted,broadly rounded apices.An indistinct pseudoseptum is present at the poles.This second new species is similar to Parlibellus protracta but differs in outline,especially the degree to which the headpole is protracted.In addition some species similar to Prestauroneis have been included in Parlibellus,a genus of quite different morphology.We compare the differences between these two genera,and based on published observations of valve ultrastructure we propose a new combination,Prestauroneis protractoides(Hustedt)Q.Liu & Kociolek comb.nov.Assignment to Prestauroneis of other species in Parlibellus awaits future SEM studies.Though currently a small genus,Prestauroneis may be found across a wide spectrum of environments,from fresh to brackish waters.