Wygodzinsky (1950b: 386) placed Pachycoleus in synonymy of Cryptostemma and was followed by Linnavuori. Later, Linnavuori (1984: 20) regarded Pachycoleus as a subgenus of Cryptostemma and placed in it, in addition to two European species living in mosses, also Cryptostemma gracile and Cryptostemma japonicum (both living under stones at banks of rivers, as typical Cryptostemma), Cryptostemma utnapishtim (collected at light and stated to be related to Cryptostemma gracile) and tentatively Cryptostemma titan Linnavuori from Sudan. This classification agrees with Josifov's (1967) observations and is followed here, but with regard on habitat differences (see also Štys, 1990) the problem deserves further study.
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