  We have studied the unbarred Sb galaxy with a nuclear star-forming ring, NGC
7742, by means of 2D spectroscopy, long-slit spectroscopy, and imaging, and
have compared the results with the properties of another galaxy of this type,
NGC 7217, which is studied by us earlier. Both galaxies have many peculiar
features in common: each has two global exponential stellar disks with
different scalelengths, each possesses a circumnuclear inclined gaseous disk
with a radius of 300 pc, and each has a global counterrotating subsystem,
gaseous one in NGC 7742 and stellar one in NGC 7217. We suggest that past minor
merger is the probable cause of all these peculiarities, including appearance
of the nuclear star-forming rings without global bars; the rings might be
produced as resonance features by tidally induced oval distortions of the
global stellar disks.
