Pinnularia Acrosphaeria Guide
Credit: Loren Bahls
  1. Valves with slightly gibbous center
  2. Apices broadly rounded and subcapitate
  3. Valve surface mottled

Pinnularia acrosphaeria has linear valves with an expanded center and broadly rounded, subcapitate apices. The raphe is lateral and the outer fissure of the raphe is straight. The valve surface has a mottled appearance.