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Nitzschia amphibia var. frauenfeldii has finer striae and fibulae. Denticula kuetzingii and Denticula kuetzingii var. rumrichae have valves that are more linear and not constricted in the center. In addition, Denticula kuetzingii has higher stria density (13-20 in 10µm) and fibula density (5-8 10 µm). Denticula kuetzingii var. rumrichae overlaps in length, but has a differing fibula structure.

LM scalebar = 10 µm
Nitzschia serpentiraphe LM4 Nitzschia serpentiraphe LM3 Nitzschia serpentiraphe LM5 Nitzschia serpentiraphe LM1 Nitzschia serpentiraphe LM2 Nitzschia serpentiraphe LM2 Nitzschia serpentiraphe LM1
Length Range
56-105 µm
Width Range
6.2-8.1 µm
Striae in 10 µm
11-12

Also compare to

Denticula kuetzingii

Grunow

BioData Reference
Krammer and Lange-Bertalot 2/2 Pl 99 Fig 11-23 Pl 100 Fig 1-14

Denticula kuetzingii var. rumrichae

BioData Reference
Krammer and Lange-Bertalot 2/2 Pl 100 Fig 18-22

Nitzschia amphibia fo. frauenfeldii

BioData Reference
Krammer and Lange-Bertalot 2/2 Pl 78 Fig 25-26