  Based on the Chandra data archive as of March 2016, we have identified 314
candidate active galactic nuclei in 719 galaxies located closer than 50 Mpc,
among them late-type (Hubble types Sc and later) galaxies that previously had
been classified from optical observations as containing star-forming (H II)
nuclei. These late-type galaxies comprise a valuable subsample to search for
low-mass (<~ 10^6 solar masses) central black holes. For the sample as a whole,
the overall dependence of the fraction of active nuclei on galaxy type and
nuclear spectral classification is consistent with previous results based on
optical surveys. We detect 51 X-ray cores among the 163 H II nuclei and
estimate that, very conservatively, ~74% of them with luminosities above 10^38
erg/s are not contaminated by X-ray binaries; the fraction increases to ~92%
for X-ray cores with a luminosity of 10^39 erg/s or higher. This allows us to
estimate a black hole occupation fraction of >~ 21% in these late-type, many
bulgeless, galaxies.
