2026-07-072026-07-07http://salesiana.dossiersoluciones.com/handle/123456789/3703The Seyfert galaxies with Z-shaped emission filaments in the Narrow Line Region (NLR) are considered. We assume that observable Z-shaped structures and velocity pattern of NLR may be explained as tridimensional helical waves in the ionization cone.To appear in IAU Colloq. 184, AGN Surveys, ed. R. F. Green, E. Ye. Khachikian, & D. B. Sanders (San Francisco: ASP), in press. 2 pages, 1 EPS figureAstrophysicstext