Frustulia Krammeri Guide
Credit: Carrie Graeff
  1. Gap in striae at apices
  2. Valves strongly rhomboid
  3. Valve margin slightly constricted at apices
  4. Longitudinal ribs and raphe curved slightly
  5. Transapical striae wavy and convergent near apices

Valves are strongly rhomboid, with a slight constriction at the valve apices. The longitudinal ribs and raphe curve slightly in the same direction. Near the apices, the striae become moderately wavy and then convergent at the apices. Striae do not circumradiate the poles.