  The Southern HII Region Discovery Survey (SHRDS) is a 900 hour Australia
Telescope Compact Array 4-10 GHz radio continuum and radio recombination line
(RRL) survey of Galactic HII regions and infrared-identified HII region
candidates in the southern sky. For this data release, we reprocess all
previously published SHRDS data and include an additional ~450 hours of
observations. The search for new HII regions is now complete over the range 259
deg < Galactic longitude < 346 deg, |Galactic latitude| < 4 deg for HII region
candidates with predicted 6 GHz continuum peak brightnesses >30 mJy/beam. We
detect radio continuum emission toward 730 targets altogether including
previously known nebulae and HII region candidates. By averaging ~18 RRL
transitions, we detect RRL emission toward 206 previously known HII regions and
436 HII region candidates. Including the northern sky surveys, over the last
decade the HII Region Discovery Surveys have more than doubled the number of
known Galactic HII regions. The census of HII regions in the WISE Catalog of
Galactic HII Regions is now complete for nebulae with 9 GHz continuum flux
densities > 250 mJy. We compare the RRL properties of the newly discovered
SHRDS nebulae with those of all previously known HII regions. The median RRL
full-width at half-maximum line width of the entire WISE Catalog HII region
population is 23.9 km/s and is consistent between Galactic quadrants. The
observed Galactic longitude-velocity asymmetry in the population of HII regions
probably reflects underlying spiral structure in the Milky Way.
