Navicula Viridula Guide
Credit: Marina Potapova
  1. Valves lanceolate to linear-lanceolate
  2. Apices subrostrate
  3. Valves 11.2-13.5 μm wide
  4. Central nodule asymmmetric
  5. External proximal raphe ends bent toward primary side

Valves are lanceolate to linear-lanceolate with subrostrate apices. Central area is asymmetric; trapezoid on primary side, semi-circular on secondary side. External proximal raphe ends are slightly dilated and bent toward the primary side of the valve. The central nodule is asymmetrically expanded on the internal valve surface to the primary side. Striae are radiate in the valve center, becoming convergent at the apices.