Frustulia Guide2
Credit: Carrie Graeff
  1. Valve with distinct median longitudinal ribs
  2. Ribs form a single tip at valve ends
  3. Raphe present between longitudinal ribs
  4. Striae fine, punctate, forming transapical and longitudinal rows

Frustulia valves are rhomboid to linear-lanceolate with straight to undulate margins. The striae are composed of fine areolae, arranged into patterns that appear to form both apical and transapical rows.The genus possesses distinct median, longitudinal ribs that extend most of the length of the valve. The raphe is located between the longitudinal ribs. At the valve terminus, the ribs form a single tip, or porte-crayon. The proximal and distal raphe ends are not clearly observed with light microscopy. Living cells possess one H-shaped plastid.

Frustulia grows in benthic habitats as single cells or as colonies in mucilaginous tubes. Species of Frustulia are widespread in North America. Cells reach their greatest abundance in waters such as seepage lakes where the water is slightly acidic, dissolved organic carbon (DOC) is high, and specific conductivity is relatively low.