Argynnia lacustris Wailes, 1912*
Basionym: Argynnia dentistoma var. lacustris Wailes, 1912
Diagnosis: Shell pyriform, slightly elongated toward the pseudostome, which is proportionally small, crenulated, and abruptly truncated. Test very transparent, covered with siliceous, angular platelets and granules of various sizes, often intermixed with diatom frustules.
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.
Specimens from a population in Killarney National Park, Ireland, measured 124–147 µm (Siemensma, 2026, unpublished).
Ecology: Sphagnum.
*) Argynnia dentistoma var. lacustris Wailes, 1912 is correctly treated as Argynnia lacustris Wailes, 1912. No new name needs to be established in this case under the International Code of Zoological Nomenclature. Because the name was published before 1961 using the abbreviation var., it is deemed subspecific under Article 45.6.4, unless explicitly proposed as infrasubspecific. As a species-group name, it is simultaneously established at both species and subspecies rank under the Principle of Coordination (Art. 46.1), with the same author, date, and name-bearing type. Accordingly, when treated at species rank, the correct name is Argynnia lacustris Wailes, 1912.
