Argynnia dentistoma var. hesperia  Wailes, 1913

Diagnosis: This variety is distinguished from the A. dentistoma var. lacustris Wailes, by the absence of any definite neck and by the structure of the test, which consists of small plates with regular outlines. Proportions of the test vary considerably, the width ranging from 0.6-0.8 of the length, the narrow tests having an ovoid outline. The average of 13 tests gave: length 175 µm, width 128 µm, aperture 38 µm; two tests each 170 µm in length measured 100 and 140 µm in width respectively.

Dimensions: According to Wailes (1913): Shell length 155—190 um; width 100—142 um; aperture 32—50 um, thickness 0.5—0.6 of the width.

Habitat: Sphagnum.

Geographical distribution: South-America (Puntas Arenas, Mt. Corovada, Rio de Janeiro).