Pinnularia rexlowei guide
  1. Valves linear, slightly inflated in the middle
  2. Apices capitate-cuneate
  3. Axial area 1/4–1/3 of valve width
  4. Longitudinal line crosses striae half-way
  5. Short spines at valve face–mantle junction

Valves are linear, slightly inflated in the middle, with capitate-cuneate apices. Axial area is linear, 1/4–1/3 the valve width. A longitudinal line transects the striae approximately half-way between the axial area and the margin. Short conical spines, straight or slightly bent in the direction of valve apices are located at the valve face–mantle junction.