Frustulia Vulgaris Guide
Credit: Carrie Graeff
  1. Longitudinal ribs incomplete at the valve center
  2. Striae slightly radiate at valve center
  3. Central area ovoid
  4. Valves slightly rhomboid, with rostrate apices

The valves are linear-lanceolate-rhomboid, with rostrate apices. The striae are slightly radiate at the center of the valve, parallel or slightly convergent near the apices, and convergent at the apices. The longitudinal ribs are discontinuous at the center of the valve and do not fuse with the central nodule. The central area is ovoid in shape. The distal, external raphe fissures form a small Y-shape, usually visible only with SEM.