Frustulia Inculta Guide
Credit: Carrie Graeff
  1. Striae do not circumradiate apices
  2. Longitudinal ribs and raphe curved
  3. Longitudinal ribs moderately or slightly constricted at central nodule
  4. Longitudinal striae wavy
  5. Transapical striae parallel

The striae are not circumradiate at the valve apices. The longitudinal ribs and raphe are noticeably curved. The longitudinal ribs are moderately or slightly constricted at the central nodule. Longitudinal striae are present but are very wavy. The transapical striae are generally parallel.