Slit positions superposed on the Hα images. The length of each line corresponds to the length of the abscissa in Fig. 2. (a) NGC 2366: the Hα image is taken from Fig. 1 in Roy et al. (1991). The length of the line corresponds to 160﹩\arcsec﹩. (b) Holmberg II: the Hα image is taken from Fig. 1 in Hodge et al. (1994). The length of the line corresponds to 250﹩\arcsec﹩. (c) IC 2574: the Hα image is taken from Fig. 3 in Miller & Hodge (1994). The length of the line corresponds to 200﹩\arcsec﹩. (d) WLM: the Hα image is taken from Fig. 1a in Hodge & Miller (1995). The length of the line corresponds to 200﹩\arcsec﹩.