A Minutissiumum Guide
Credit: Marina Potapova
  1. Striae radiate throughout both valves
  2. Areolae typically not visible in LM
  3. Valves linear-lanceolate

Raphe valve concave, rapheless valve convex. Valves linear-lanceolate, with subrostrate or subcapitate ends. Striae radiate throughout both valves, uniseriate. Areolae usually not discernible under LM. Axial area narrow, only slightly widened in the valve center. Centermost striae of raphe valve often more widely spaced than in the rest of the valve, considered to be a 'fascia'.