  We have created a new, clean catalogue of extragalactic non-nuclear X-ray
sources by correlating the 3XMM-DR4 data release of the XMM-Newton
Serendipitous Source Catalogue with the Third Reference Catalogue of Bright
Galaxies and the Catalogue of Neighbouring Galaxies, using an improved version
of the method presented in Walton et al. (2011). Our catalogue contains 1,314
sources, of which 384 are candidate ultraluminous X-ray sources (ULXs). The
resulting catalogue improves upon previous catalogues in its handling of
spurious detections by taking into account XMM-Newton quality flags. We
estimate the contamination of ULXs by background sources to be 24 per cent. We
define a 'complete' subsample as those ULXs in galaxies for which the
sensitivity limit is below $10^{39}$ erg/s and use it to examine the hardness
ratio properties between ULX and non-ULX sources, and ULXs in different classes
of host galaxy. We find that ULXs have a similar hardness ratio distribution to
lower-luminosity sources, consistent with previous studies. We also find that
ULXs in spiral and elliptical host galaxies have similar distributions to each
other independent of host galaxy morphology, however our results do support
previous indications that the population of ULXs is more luminous in
star-forming host galaxies than in non-star-forming galaxies. Our catalogue
contains further interesting subpopulations for future study, including
Eddington Threshold sources and highly variable ULXs. We also examine the
highest-luminosity (L$_X$ > $5 \times 10^{40}$ erg/s) ULXs in our catalogue in
search of intermediate-mass black hole candidates, and find nine new possible
candidates.
