Diploneis smithii and D. ovalis have narrower longitudinal canals. Diploneis ovalis also have uniseriate striae and larger central areas. Diploneis dilatata has biseriate striae, but narrower longitudinal canals and wider axial area.

LM scalebar = 10 µm
Diploneis finnica LM1 Diploneis finnica LM2 Diploneis finnica LM3 Diploneis finnica LM4 Diploneis finnica LM5 Diploneis finnica LM6
Length Range
52-107 µm
Width Range
33-53 µm
Striae in 10 µm

Diploneis ovalis

(Hilse) Cleve 1891

Diploneis Ovalis 1 Diploneis Ovalis 2 Diploneis Ovalis 3 Diploneis Ovalis 4 Diploneis Ovalis 5 Diploneis Ovalis 6 Diploneis Ovalis 7
Length Range
32.5-58.7 µm
Width Range
20.7-32.6 µm
Striae in 10 µm

Also compare to

Diploneis smithii

(Bréb. ex W.Sm.) Cleve

Diploneis dilatata

(Peragallo) Lange-Bertalot and Fuhrmann