Compare

The valve face of H. triquetra appears to be more of a single triangle in shape, with the 3 distinct apices terminating in pseudocelli.

LM scalebar = 10 µm
Hywhamp  Ill 2013 132 1 Hywhamp  Mbe959B 2 Hywhampoensis  Ill2013 132 2 Hywhamp  Mbe959B 1A Hywhampoensis  Ill2013 132 3 Hywhamp  Ansp 115511 1
Diameter
35.0-72.5 µm

Also compare to

Hydrosera triquetra

G.C.Wall.

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