Pinnularia dariana guide
  1. Valves linear-lanceolate, barely triundulate
  2. Valve apices broad, rounded
  3. Axial area broad
  4. Longitudinal line present

Valves are linear-lanceolate, barely triundulate. Valve ends are broad and rounded. Axial area is linear-lanceolate, 1/4-1/3 of the valve width. A longitudinal line clearly visible under LM. crosses the striae, approximately mid way between the longitudinal axis and the valve margin.