Epithemia sorex has smaller valves (less than 9 µm wide), 6 to 8 costae in 10 µm, and usually 2 (sometimes 3) striae between costae. Valves of E. cistula do not have recurved apices and the branches of the raphe canal follow a straighter line to the apices closer to the dorsal margin.

LM scalebar = 10 µm
Epithemia Smithii1A Epithemia Smithii2A Epithemia Smithii3A Epithemia Smithii4A Epithemia Smithii5A Epithemia Smithii6A Epithemia Smithii7A
Length Range
30.3-85.1 µm
Width Range
9.4-13.3 µm
Striae in 10 µm

Epithemia sorex

Kütz. 1844

Esor Mo000125 8Ed 1 Esor Ih0440 1Ed 1 Esor Mo000125 5Ed Esor Ih0440 2Ed 1 Esor Mo000125 7Ed Esor Mo000125 4Ed Esor Mo000125 6Ed
Length Range
20-33 µm
Width Range
7.3-9 µm
Striae in 10 µm

Also compare to

Epithemia cistula

(Ehrenb.) Ralfs