Argynnia dentistoma (Penard, 1890)
Diagnosis: shell colorless, ovoid, slightly compressed laterally and composed of oval, elongated shell plates which do not overlap; plates united by minute chitinous bridges; aperture oval; collar ornamented with circular scales, giving the impression of a denticulated border.
Ecology: Sphagnum and other mosses.
Dimensions: length 70-115 µm, my measurements 69-117 µm.
Remarks: Cash et al. (1909) stated that the shell of this species fractured when subjected to pressure, whereas those of N. collaris and N. tincta were simply distorted. The shell of Argynnia dentistoma is of a more rigid construction. Three varieties of this species which differ in size and shape of the aperture and shell have been described by Deflandre (1936) in his review of the genus.