Tetraphidaceae. Genus Tetraphis
1. Setae straight to weakly bent at middle; setae cells smooth or with solitary papillae; perichaetial leaves straight when wet —
1. T. pellucida
Widespread epixylic moss throughout the boreal and hemiboreal zones of Russia, absent from the permafrost regions and Far Eastern islands and replaced by T. geniculata. Occasionally grows in other zones and on other substrates, such as wet soil rich in humus and on sandstone.
— Setae clearly and distinctly bent at middle; setae cells prorate above the middle bend; perichaetial leaves reflexed when wet —
2. T. geniculata
Common in Sakhalin and Kuril Islands but otherwise rare in the mainland of Russian Far East. The species occurs in the same habitats as T. pellucida, and in the regions of co-occurence can cause identification problems because its diagnostic characters sometimes vary within otherwise homogeneous tufts.