Compare

Pinnularia dactylus has smaller valves less than 38 µm in width and greater than 6 striae in 10 µm. Valves of P. mesogongyla are also less than 38 µm in width, a smaller central area and 5-6 striae in 10 µm. Valves of Pinnularia viridis are less than 30 µm wide and and 6-7 striae in 10 µm. Valves of P. flexuosa have broadly rounded apices.

LM scalebar = 10 µm
Pinnularia gigas LM1 Pinnularia gigas LM2 Pinnularia gigas LM3 Pinnularia gigas LM4 Pinnularia gigas LM5
Length Range
172.7-297.0 µm
Width Range
39.3-64.0 µm
Striae in 10 µm
4-5

Also compare to

Pinnularia dactylus

Ehrenb. 1843

Pinnularia mesogongyla

Ehrenb. 1843

Pinnularia viridis

(Nitzsch) Ehrenb. 1843

Pinnularia flexuosa

Cleve 1895