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Fragilariforma nitzschioides, F. virescens, and F. acidobiontica all have linear valves with protracted ends, but the latter differs by having a lower stria density and the lack of a distinct sternum. Similar in valve outline to S. exiguiformis, F. acidobiontica differs by its more narrow apices, lower stria density and greater length.

LM scalebar = 10 µm
Ansp  Gc 54250  Fragilariforma Acidobiota  T7 Ansp  Gc 54250  Fragilariforma Acidobiota  T1 Ansp  Gc 54250  Fragilariforma Acidobiota  T5 Ansp  Gc 54250  Fragilariforma Acidobiota  T3 Ansp  Gc 54250  Fragilariforma Acidobiota  T6 Ansp  Gc 54250  Fragilariforma Acidobiota  T4
Length Range
32-67 µm
Width Range
3-4 µm
Striae in 10 µm
12-14 in the center valve, 14-15 at the ends

Fragilariforma nitzschioides

(Grunow) Lange-Bert. 2011

Fragilariforma nitzschioides LM3 Fragilariforma nitzschioides LM4 Fragilariforma nitzschioides LM5 Fragilariforma nitzschioides LM6 Fragilariforma nitzschioides LM2 Fragilariforma nitzschioides LM1 Fragilariforma nitzschioides LM7
Length Range
19-54 µm
Width Range
3.5-5.5 µm
Striae in 10 µm
18-25

Fragilariforma virescens

(Ralfs) D.M.Williams and Round 1988

Fragilariforma virescens LM6 Fragilariforma virescens LM3 Fragilariforma virescens LM1 Fragilariforma virescens LM4 Fragilariforma virescens LM2 Fragilariforma virescens LM5
Length Range
15-60 µm
Width Range
6.5-7.0 µm
Striae in 10 µm
20-22

Stauroforma exiguiformis

(Lange-Bert.) Flower, Jones and Round 1996

Stauroforma exiguiformis LM4 Iwb 0040 06072015 08 Cl Stauroforma exiguiformis LM1 Stauroforma exiguiformis LM3 Stauroforma exiguiformis LM5 Stauroforma exiguiformis LM2
Length Range
4-22 µm
Width Range
3-4 µm
Striae in 10 µm
16-20

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