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Guide to Pinnularia decrescens

(Grunow) Krammer 2000

Pinnularia decrescens guide
  1. Valve margin slightly triundulate
  2. Central valve expansion slightly wider than distal expansion
  3. Apices rostrate
  4. Central area large
  5. Striae radiate in the middle, convergent toward the apices

Valves have a slightly triundulate margin, with the central expansion slightly wider than the distal expansion. Apices are rostrate. The axial area is linear-lanceolate, 1/4-1/3 of the valve width. The central area is large and elliptic to rhombic. Striae are radiate in the middle, becoming strongly convergent toward the apices.