  We have investigated the doping dependence of the penetration depth vs.
temperature in electron doped Pr$_{2-x}$Ce$_x$CuO$_{4-\delta}$ using a model
which assumes the uniform coexistence of (mean-field) antiferromagnetism and
superconductivity. Despite the presence of a $d_{x^2-y^2}$ pairing gap in the
underlying spectrum, we find nodeless behavior of the low-$T$ penetration depth
in underdoped case, in accord with experimental results. As doping increases, a
linear-in-$T$ behavior of the penetration depth, characteristic of d-wave
pairing, emerges as the lower magnetic band crosses the Fermi level and creates
a nodal Fermi surface pocket.
