Achnanthes Undulorostrata Guide
Credit: Rex Lowe
  1. Valves triundulate
  2. Ends broadly rounded
  3. Proximal ends slightly unilaterally deflected
  4. Rapheless valve with eccentric axial area

Valves are triundulate with broadly rounded ends. The raphe valve has a nearly rectangular central area, extending to the valve margins. The proximal raphe ends are deflected slightly unilaterally deflected. The rapheless valve has an axial area positioned near the valve margin.