Staurodesmus convergens (EHRENB. ex RALFS) TEILING Synonym: Arthrodesmus convergens EHRENB. ex RALFS Cells are wider than long, the cell halves have elliptical shapes. The cell halves are laterally covered with large inward bent spines. The central cuts are strongly broadened towards the periphery. Dimension: Length 35 â 55 µm, width 50 â 80 µm (including spines) Ecology: In acidic to medium acidic fens. Occurrence: Ubiquitous common