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Scanning electron microscopy studies of nematode specimens of Cystidicola farionis Fischer, 1798, a swimbladder parasite mainly of salmonids, made it possible to describe in detail the cephalic structure as well as some additional morphological features of this widely distributed nematode and, accordingly, to correct the generic diagnosis of Cystidicola Fischer, 1798. Similarly to species of the most related genera Comephoronema Layman, 1933 and Salvelinema Trofimenko, 1962, the males of C. farionis (a type species of the genus) possess well-developed ventral precloacal ridges (area rugosa). As shown by this study, the genus Cystidicola differs from Comephoronema and Salvelinema mainly in the structure of the mouth, particularly in the presence of four well-demarcated labia, large circumoral teeth, and in the character of pseudolabia.