  We present line-strength measurements for 74 early-type galaxies in the core
of the Coma cluster reaching down to velocity dispersions, sigma, of 30 km/s.
The index-sigma relations for our sample, including galaxies with sigma<100
km/s (low-sigma), differ in shape depending on which index is used. We notice
two types of relations for the metallic indices: one showing a break in the
slope around ~100 km/s, and another group with strong linear relations between
an index and log sigma. We find no connection between the behavior of
index-sigma relations with either alpha- or Fe-peak elements. However, we find
indications that the relations are tighter for indices which do not depend on
the micro-turbulent velocities of stellar atmospheres. We confirm previous
results that low-sigma galaxies including dE/dS0s are on average younger, less
metal rich, and have lower [alpha/Fe] in comparison to E/S0s. Our data show
that these trends derived for high-sigma galaxies extend down to dE/dS0s. This
is a factor of ~2 lower in sigma than previously published work. We confirm
that the observed anti-correlation between age and metallicity for high-sigma
galaxies is consistent with the effects of correlated errors. Low-sigma
galaxies also show a similar relation between age and metallicity as a result
of correlated errors. However, they are offset from this relationship so that,
on average, they are less metal rich and younger than their high-sigma
counterparts.
