Frustulia Bahlsii Guide
Credit: David Burge
  1. Valves lanceolate
  2. Longitudinal ribs blunt at apices
  3. Central nodule constricted

Valves are large (123-195 ┬Ám) and lanceolate. The longitudinal ribs terminate in a distinct, blunt end at the valve apices. The central nodule is constricted. The porte-crayon typical of Frustulia is absent.