Psammothidium Semiapertum Guide
Credit: Marina Potapova
  1. Valves elliptic
  2. Striae 22-24 in 10 µm
  3. Areolae 25 in 10 µm
  4. Rapheless valve may have asymmetric central area

Valves are elliptic. Both valves have narrow linear axial areas and transversely rectangular central areas. The central area on the rapheless valve may be asymmetric. The raphe is filiform and straight. There are 25 areolae in 10 μm along the stria.