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Guide to Gomphoneis mammilla

(Ehrenb.) Cleve 1894

Gomphoneis Mammila Guide
Credit: Pat Kociolek
  1. Valves distinctly clavate
  2. Striae 7-9 in 10 µm
  3. Headpole subrostrate to broadly rounded
  4. Two spines at the headpole

Valves are distinctly clavate in shape. The axial area is relatively narrow, straight, widening only slightly to form a narrowly elliptical central area with a single stigma. The raphe is lateral, weakly undulate. External proximal raphe ends are dilated. Striae are evidently doubly-punctate, radiate the length of the valve. Longitudinal lines are evident on either side of the axial area, positioned 1/5-1/4 the way from the valve margin towards the axial area. At the headpole are two conspicuous spines. The footpole bears distinct apical pore fields. Septa and pseudosepta are present at the apices.