Gliwiczia Guide
Credit: Marina Potapova
  1. Frustules monoraphid
  2. Valves elliptic
  3. Striae and areolae more dense on raphe valve than on rapheless valve
  4. Internal cavum on both valves
  5. Stauros on both valves

Gliwiczia was established in 2013 to accommodate Achnanthes/Planothidium calcar and similar species. This genus has monoraphid frustules with a slightly concave raphe valve and almost flat, rapheless valve. Valves are elliptic. Both valves bear an internal cavum and a fascia. Striae and areolae are considerably more dense and smaller on the raphe valve as compared to the rapheless valve. The raphe is straight, but its distal ends are slightly turned to opposite sides. Terminal raphe fissures are absent. External proximal raphe ends are slightly expanded, internal ends are non-coaxial as in all Achnanthidiaceae.

Gliwiczia is mostly found in cold oligotrophic waters. So far, only one species, G. calcar has been reported from North America.