  The recently-discovered stellar system in Canis Major is analysed using
He-burning Red Clump stars as tracers. Canis Major turns out to be the
strongest and most spatially confined overdensity of the whole Galactic Disc,
both in terms of number density and of statistical significance. When projected
onto the Galactic Plane, it appears as an elongated and compact overdensity
extending from l ~ 200 to l ~ 280 with a roundish core toward l ~ 240. We find
that the main body of the system has an integrated absolute magnitude M_V=-14.4
+/- 0.8, a central surface brightness \mu_{V,0} = 24.0 +/- 0.6 mag/arcsec^2 and
a line-of-sight profile peaked at D_{sun}=7.2 +/- 1.0 kpc with Half Width at
Half Maximum ~ 2.0 kpc, in excellent agreement with the results obtained with
widely different tracers (M giants and Main Sequence stars) in previous
analyses. The mean distance to the main body of Canis Major is observed to
increase with increasing Galactic longitude, from D_{sun} ~ 6.3 kpc at l ~ 225,
to D_{sun} ~ 9.3 kpc at l ~ 265, in good agreement with the predictions of our
more recent N-body simulation that models CMa as a dwarf galaxy being accreted
in a planar orbit onto the disc of the Milky Way. We confirm that the Canis
Major system has all the characteristics of the relic of a dwarf galaxy seen on
top of a large-scale overdensity that we detect all over the third and fourth
Galactic quadrants (180<l<360, with a strong maximum around l=290 and b> -5)
that is identified as the stellar component of the southern Galactic Warp...
(Abridged)....
