Differences between molluscan assemblages occurring in loess series of the Younger Pleistocene bear no distinct relation to the age of the sediments. The assemblages recorded from the last two cold periods (Saalian, Vistulian) comprise the same species, differences in the species composition among the faunae of various localities being controlled by environmental factors. This conclusion stems from the studies carried out by V. Ložek in Czechoslovakia, J. J. Puissegur in France, M. Wag­ner in Hungary, as well as from those carried out in Roland, a.o. in the profiles at Odonów and in the Przemyśl region.