  Applying the microcanonical definition of entropy to a weakly interacting and
self--gravitating neutralino gas, we evaluate the change in the local entropy
per particle of this gas between the freeze out era and present day virialized
halo structures. An ``entropy consistency'' criterion emerges by comparing the
obtained theoretical entropy per particle of the virialized halos with an
empirical entropy per particle given in terms of dynamical halo variables of
actual galactic structures. We apply this criterion to the cases when
neutralinos are mostly B-inos and mostly Higgsinos, in conjunction with the
usual ``abundance'' criterion requiring that present neutralino relic density
complies with $0.2<\Omega_{{\tilde\chi^1_0}} < 0.4$ for $h\simeq 0.65$. The
joint application of both criteria reveals that a much better fitting occurs
for the B-ino than for the Higgsino channels, so that the former seems to be a
favored channel along the mass range of $150 \hbox{GeV} < m_{{\tilde\chi^1_0}}
< 250 \hbox{GeV}$. These results are consistent with neutralino annihilation
patterns that emerge from recent theoretical analysis on cosmic ray positron
excess data reported by the HEAT collaboration. The suggested methodology can
be applied to test other annihilation channels of the neutralino, as well as
other particle candidates of thermal WIMP gas relics.
