Diatoms of North AmericaDiatoms of North America
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Guide to Diatoma problematica

Lange-Bert. 1993

Diatoma problematica guide
  1. Valves elliptic to linear-lanceolate
  2. Apices rounded
  3. Transapical ribs 6-8 in 10 µm
  4. Rimoportula within transapical rib

Valves are elliptic to linear-lanceolate with rounded or slightly set-off apices.  Axial area is linear, very narrow. Transapical ribs number 6-8 in 10 µm. A rimportula is positioned within a transapical rib at one, or both, valve apices.