Platessa Lutheri Guide
Credit: Marina Potapova
  1. Valves elliptic
  2. Striae on raphe valve uniseriate, 25-29 in 10 μm
  3. Striae on rapheless valve biseriate, 12-15 in 10 μm
  4. Central area on raphe valve bow-tie-shaped
  5. Axial area on rapheless valve wide, elliptic-lanceolate

Valves are elliptic. The raphe valve has a narrow linear axial area and a wide, bow-tie-shaped central area. The striae on the raphe valve are uniseriate and strongly radiate. The rapheless valve has a wide lanceolate axial area bordered by short and broad biseriate striae.