Corythion dubium Taranek, 1871
Diagnosis: shell ovoid, composed of approximately four hundred oval shell-plates, irregularly arranged, very small and usually overlapping each other; aperture sub-terminal, oval and invaginated; about thirty small, oval, apertural-plates surround the aperture, each carrying a median dorsal tooth.
Dimensions: Length 33-43 µm; breadth 25; mouth 10 µm; shell-plates length 2.9-3.4, width 1.5-1.9; diameter of apertural-plates 0.9-1.1 µm.
Ecology: Sphagnum and mosses.
Remarks: The apertural-plates are similar to those seen in Trinema enchelys and T. lineare. Differences in the size of the shell are illustrated by Cash et al., (1915).