Gomphonema Sierrianum Guide
Credit: Ian Bishop
  1. Valves clavate
  2. Headpole rostrate to subcapitate
  3. Striae radiate. to weakly radiate. to parallel
  4. Raphe lateral
  5. Axial area wide

Valves are clavate, with a rostrate to subcapitate headpole. The axial area wide and lanceolate. The raphe is lateral. Striae are short and radiate at the footpole, short and weakly radiate between apices and longer and parallel at the headpole. A single stigmoid is present.