Planothidium Lanceolatoide Guide
  1. Apices apiculate
  2. Valves 9-13 μm wide
  3. Rapheless valve with hood
  4. Raphe valve with rectangular central area

Valves are lanceolate, with apiculate apices. Width ranges from 9-13 µm. The rapheless valve has a distinct hood. The raphe valve has a nearly rectangular central area.