Cosmarium obsoletum Reinsch

Cosmarium obsoletum (Hantzsch) Reinsch Croasdale & Flint 1988, p. 81, pl. 29, figs 6,7. Fig. 4g Comments: The semicells have a disctinctive cell wall-thickening at the basal angles. Cosmarium obsoletum var. sitvense Gutwinski, which is distinguished by the presence of a large pore within the thickened basal angles of the cell wall, was also encountered and has been included here. Chloroplast in each semicell has two pyrenoids. This species is found in mildly acidic to mildly alkaline waters from aufwuchs to plankton of mires, ponds and lakes Croasdale & Flint (1988). Rated as meso-oligotrophic by Coesel & Meesters (2007). Distribution: Cosmopolitan but apparently more widespread in in tropical regions.