  An update of the set of low surface brightness galaxies is presented which
can be used to set constraints on the otherwise ambiguous decompositions of
their rotation curves into contributions due to the various components of the
galaxies. The selected galaxies show all clear spiral structure and arguments
of density wave theory of galactic spiral arms are used to estimate the masses
of the galactic disks. Again these estimates seem to indicate that the disks of
low surface brightness galaxies might be much more massive than currently
thought. This puzzling result contradicts stellar population synthesis models.
This would mean also that low surface brightness galaxies are not dominated by
dark matter in their inner parts.
