The problem of the correct interpretation of the original concept of Lentinus cyathiformis (Schaeff.) Bres. = Agaricus cyathiformis Schaeff. is analysed. The authors demonstrate, on the basis of the original protologue, that this species is identical with Pleurotus pulmonarius (Fr.) Quel. The modern interpretation of Lentinus cyathiformis, originating from Bresadola and followed by a number of contemporary authors, is erroneous: this fungus should be called Lentinus degener Kalchbr. in Fr.