  In this paper we present the first results from an on-going serendipitous
survey aiming to identify X-ray selected `normal' galaxies (i.e. not AGN
dominated) by combining archival XMM-Newton data with the Sloan Digital Sky
Survey. In the first 4.5deg2 of this program we have identified a total of 11
`normal' galaxy candidates (8 of them with optical spectroscopy) with fluxes
f_X(0.5-8keV)~1e-15-1e-13cgs. These sources are selected to have low
X-ray--to--optical flux ratio (logf_X/f_{opt}<-2), soft X-ray spectral
properties and optical spectra, when available, consistent with the presence of
a stellar ionising continuum. These sources comprise both early and late type
systems at redshifts z<0.2 with luminosities L_X(0.5-8keV)~1e39-1e42cgs. This
dataset provides the first tight constraint on the surface density of X-ray
selected `normal' galaxies at relatively bright fluxes spanning two orders of
magnitude (1e-15 - 1e-13cgs). The slope of the `normal' galaxy logN-logS in the
above flux range is estimated -1.4\pm0.3 consistent with the euclidean
prediction. We also discuss the prospects of `normal' galaxy studies at X-ray
wavelengths using both our continuously expanding survey and future X-ray
missions.
