Achnanthes Longboardia Guide
Credit: Rex Lowe
  1. Valves lanceolate
  2. Raphe valve with laterally expanded central area
  3. Rapheless valve with eccentric axial area
  4. Ends broadly rounded

Valves lanceolate, slightly swollen near the center, with broadly rounded ends. The raphe valve with a narrow axial area and wide central area, expanded laterally to the valve margins. The proximal raphe ends are slightly deflected in the same direction. The rapheless valve with an axial area positioned near the valve margin.