P Curtissimum Guide
Credit: Marina Potapova
  1. Valves elliptic to linear-elliptic
  2. Central area small
  3. Striae radiate

Valves very small, less than 10 μm in length. Valves are elliptic to linear-elliptic. 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.