  Cold + Hot Dark Matter (CHDM) $\Omega=1$ cosmological models require a total
neutrino mass $\sim 5$ eV. Because recent data support the $\nu_\mu \to
\nu_\tau$ oscillation explanation of the cosmic ray $\nu_\mu$ deficit, which
requires that $m(\nu_\mu) \approx m(\nu_\tau)$, this suggests that $m(\nu_\mu)
\approx m(\nu_\tau) \approx 2.4$ eV. The linear calculations and N-body
simulation reported here indicate that an $\Omega=1$ CHDM model with two 2.4 eV
neutrinos (designated C$\nu^2$DM) agrees remarkably well with all available
observations, but only if the Hubble parameter $h \approx 0.5$. We also show
that even one 2.4 eV neutrino raises serious difficulties for low-$\Omega$ flat
CDM models.
