Pinnularia kwacksii guide
  1. Axial area wide
  2. Valves linear
  3. Longitudinal line present
  4. Striae slightly radiate in center

Valves are linear, with broadly rounded apices. The axial area is broad, about 1/2 the width of the vale. Striae are slightly radiate in the center, slightly convergent at the apices, and a longitude line crosses the striae.