The marine, littoral and brackish-water tubificid genus Spiridion Knöllner, 1935 (sub-family Phallodrilinae) is reviewed and re-defined. S. insigne Knöllner, 1935 is reported from the British Isles (W Scotland) for the first time. The male efferent ducts of S. insigne and S. modricensis (Hrabe, 1973) comb.n, are described. In both species, relatively short, ciliated vasa deferentia enter apical, ental ends of long cylindrical atria. In each atrium can be distinguished a small, granulated and ciliated, ental atrial ampulla, and a long non-granulated and non-ciliated, ectal ejaculatory duct. The lumen of the latter is winding, but its external surface is not folded. S. scrobicularae Lastockin, 1937 is considered as a 'species dubia'.
