Argynnia dentistoma var. lacustris Wailes, 1912

Diagnosis: Shell pyriform, a little elongate towards the pseudostome that is proportionally smaller and crenulated, abruptly cut off. Shell very transparent, covered with siliceous, angular platelets and granules of various sizes, often mixed with diatom frustules.
This variety differs from A. dentistoma var. lacustris, due to the shape of its test and the relative size of the aperture, in turn having the largest size of the A. dentistoma complex.

Dimensions: According to Wailes (1912): Shell length 100 µm; width 80 µm; aperture 20 µm. Other authors: length 120—206 µm, width 100—143 µm.

Habitat: Sphagnum.