Mass-to-light ratio of the sech component as a function of line width. Dwarf irregulars (dIs) are marked with open circles, and blue compact dwarfs (BCDs) are flagged by solid circles. Individualized mass-to-light ratios were determined from the deviations in surface brightness from the norms expected for virialized systems. The horizontal dashed line is the value of the mass-to-light ratio which was computed for the entire sample in establishing the potential plane of Fig. 3.