Nupela Subrostrata Guide
Credit: Marina Potapova
  1. Valves linear to linear-lanceolate
  2. Raphe absent on one valve
  3. Striae 20-24 in 10 μm
  4. Central area on raphe valve round or ellitpical

Valves are linear to linear-lanceolate with slightly drawn-out ends. The raphe is absent on one valve. The rapheless valve has a narrowly rhomboid axial area, which sometimes widens in the middle portion of the valve to form an asymmetrical central area. The raphe valve has a narrowly lanceolate axial area and circular or elliptical central area. Striae are radiate through both valves, 20-24 in 10 μm.