  We measure luminosity functions in the cores of four spiral-rich, poor
clusters of galaxies at median redshift $z = 0.016$. In the red magnitude range
-14 < M_R < -10, our data imply that the luminosity functions phi(L) \propto
L^{alpha} are steep, -1.8 < alpha < -1.6, in the central 200-300 kpc of Abell
262 and of the NGC 507 Group. Abell 194 also shows signs of a steep luminosity
function, alpha < -1.6, in this magnitude range. In Pegasus, the dwarf galaxy
density is too low to let us constrain alpha. The NGC 507 Group and Abell 194
have been interpreted as clusters that are forming today, based on morphology
and velocity structure. The high spiral galaxy fraction in Abell 262 relative
to clusters like Virgo and Coma also suggests that it is young. We therefore
suggest that steep luminosity functions in the range -14 < M_R < -10 may be a
universal feature of young clusters and possibly of the field. If this is true,
then the observed paucity of gas-rich galaxies in such environments suggests
that we are finding galaxies similar to the low-surface-brightness,
dark-matter-dominated dwarf spheroidal galaxies seen locally and in Virgo. This
interpration is also consistent with the distribution of colors and sizes of
the faint galaxies in Abell 262. If we are indeed detecting dwarf spheroidal
galaxies and if they are as numerous relative to bright galaxies in the field
as they are in the young clusters observed here, then the contribution of their
halos to the cosmological mass density is Omega_{dSph halo} \approx 0.01. This
is much smaller than values of Omega derived from dynamical measurements.
