Pinnularia Borealis Guide
Credit: Loren Bahls
  1. Valves linear to linear-elliptic
  2. Apices broadly rounded
  3. Proximal raphe deflected laterally

Valves are small and linear to linear-elliptic, with rounded apices. The proximal raphe ends are laterally deflected. Maximum valve width is about 10 µm. Striae are distinctly broad and number 5-6 in 10 µm.