P Curtissimum Guide
Credit: Marina Potapova
  1. Valves elliptical to linear-elliptical
  2. Central areas on both valves small
  3. Striae radiate

Valves are elliptical to linear-elliptical. Valves very small, less than 10 μm in length. Both valves have small transversely elongated central areas. The raphe is straight, without terminal fissures. Striae are radiate on both valves, 27-31 in 10 µm.