  We present the emission-line fluxes and kinematics of 48 representative
elliptical and lenticular galaxies obtained with our custom-built
integral-field spectrograph SAURON. Hb, [OIII], and [NI] emission lines were
measured using a new procedure that simultaneously fits both the stellar
spectrum and the emission lines. Using this technique we can detect emission
lines down to an equivalent width of 0.1A set by the current limitations in
describing galaxy spectra with synthetic and real stellar templates, rather
than by the quality of our spectra. Emission is detected in 75% of our sample
galaxies, and comes in a variety of resolved spatial distributions and
kinematic behaviours. The ionised-gas kinematics is rarely consistent with
simple coplanar circular motions. However, the gas almost never displays
completely irregular kinematics, generally showing coherent motions with smooth
variations in angular momentum. In the majority of the cases the gas kinematics
is decoupled from the stellar kinematics, and in half of the objects this
decoupling implies a recent acquisition of gaseous material. Over the entire
sample however, the distribution of the mean misalignment values between
stellar and gaseous angular momenta is inconsistent with a purely external
origin. Consistent with previous studies, the presence of dust features is
always accompanied by gas emission while the converse is not always true. A
considerable range of values for the [OIII]/Hb ratio is found both across the
sample and within single galaxies. Despite the limitations of this ratio as an
emission-line diagnostic, this finding suggests either that a variety of
mechanisms is responsible for the gas excitation in E and S0 galaxies or that
the metallicity of the interstellar material is quite heterogeneous.
