  Using a hydrodynamic approach to describe Pb+Au collisions at 158 AGeV/c, we
analyze e+e- yields from matter containing baryons in addition to mesons. We
employ e+e- production rates from two independent calculations, which differ
both in their input physics and in their absolute magnitudes, especially in the
mass range where significant enhancements over expected backgrounds exist in
the CERES data. Although the presence of baryons leads to significant
enhancement of e+e- emission relative to that from mesons-only matter, the
calculated results fall below the data in the range 400 < M_ee/MeV < 600, by a
factor of 2-3. Since the calculated e+e- spectra are relatively insensitive to
the equation of state for initial conditions that fit the observed hadronic
spectra, either in-medium modifications of the e+e- sources more significant
than so far considered, or the presence of hitherto unidentified additional
sources of e+e- is indicated.
