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Cyclotella meneghiniana is larger, and lacks the distinctive marginal fultoportulae.

LM scalebar = 10 µm
Cyclotella atomus LM2 Cyclotella atomus LM6 Cyclotella atomus LM7 Cyclotella atomus LM9 Cyclotella atomus LM8 Cyclotella atomus LM3
Diameter
5-7.5 µm
Striae in 10 µm
16-18

Cyclotella meneghiniana

Kütz. 1844

Cy Meneghiniana 15624A 09212015 07 Cl Cy Meneghiniana 15640A 10132015 08 Cl Cy Meneghiniana 15540A 09172015 04 Cl Cy Meneghiniana 15615A 08242015 11 Cl Cy Meneghiniana 15596A 09042015 24 Cl Cy Meneghiniana 15540A 09172015 21 Cl
Diameter
6.24-18.12 µm
Striae in 10 µm
7-8 (chambered striae by circumference)