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Eunotia triodon may be distinguished from other large species of Eunotia with dorsal undulations by its moderatly arched valves and a consistent three broadly rounded undulations on the dorsal margin. Eunotia semicircularis may also have three undulations, but they are deeper undulations than E. triodon. Note that the degree of undulation (broad vs. deep) may be more relevant to identification than the number of undulations in distinguishing taxa.

LM scalebar = 10 µm
Eunotia triodon LM5 Eunotia triodon LM6 Eunotia triodon LM4 Eunotia triodon LM1 Eunotia triodon LM7 Eunotia triodon LM2 Eunotia triodon LM3
Length Range
47-74 µm
Width Range
15-23 µm
Striae in 10 µm
15-18 near valve center, 19-21 near the ends

Eunotia diadema

Ehrenb. 1837

Eunotia diadema LM1 Eunotia diadema LM2 Eunotia diadema LM3 Eunotia diadema LM4 Eunotia diadema LM5 Eunotia diadema LM6 Eunotia diadema LM7
Length Range
34-65 µm
Width Range
14-26 µm
Striae in 10 µm
7-10 in the valve center, 12-17 near the apices

Eunotia serra

Ehrenb. 1837

Eunotiaserra1 Eunotiaserra2 Eunotiaserra3 Eunotiaserra4 Eunotiaserra5 Eunotiaserra6 Eunotiaserra7
Length Range
60-134 µm
Width Range
18-24 µm
Striae in 10 µm
9-13 in the valve center, 14-19 near the apices

Eunotia tetraodon

Ehrenb. 1838

Eunotiatet1 Eunotiatet2 Eunotiatet3 Eunotiatet4 Eunotiatet5 Eunotiatet6
Length Range
37-51 µm
Width Range
14.2-18.8 µm
Striae in 10 µm
8-10 in the valve center, 12-15 at the apices

Eunotia hexaglyphis

Ehrenb. 1854

Eunotia Hex1 New Eunotia Hex2 Eunotia Hex3  New Eunotia Hex4 Eunotia Hex5 Eunotia Hex6 Eunotia Hex7
Length Range
27.1-48.9 µm
Width Range
8.6-12.3 µm
Striae in 10 µm
13-17

Also compare to

Eunotia semicircularis