T. arcula, Sjøforsen, Norway, 2023
Trigonopyxis arcula Penard, 1912
Diagnosis. Shell brownish, hemispherical; pseudostome central, invaginated, frequently triangular but more often irregular, surrounded by a distinct ring of organic cement; nucleus ovular.
Dimensions: Diameter of shell, my measurements: 87—173 µm. Within a population the size of the shells can vary considerably.
Habitat: Feeding on bacteria and fungi. Common in acid forest soil, litter, mosses (e.g. Sphagnum).
T. arcula, lateral view; Sjøforsen, Norway, 2023
T. arcula
The shells above are all from the same sample from Ecuador (108-173 µm)
Ecuador
T. arcula, 87 µm – Sphagnum, The Netherlands
T. arcula, 87 and 148 µm
T. arcula, c. 110 µm
Austria