  The in-plane magnetic penetration depth, $\lambda (T)$, was measured down to
0.4 K in single crystals of electron-doped superconductors,
Pr$_{1.85}$Ce$_{0.15}$CuO$_{4-\delta}$ (PCCO) and
Nd$_{1.85}$Ce$_{0.15}$CuO$_{4-\delta}$ (NCCO). In PCCO, the superfluid density
varies as $T^2$ from 0.025 up to roughly 0.3 $T/T_c$ suggestive of a d-wave
state with impurities. In NCCO, $\lambda (T)$ shows a pronounced upturn for $T
< 4$ K due to the paramagnetic contribution of Nd$^{3+}$ ions. Fits to an
s-wave order parameter over the standard BCS range ($T/T_c$ = 0.32) limit any
gap to less than $\Delta_{min} (0)/T_c = 0.57$ in NCCO. For PCCO, the absence
of paramagnetism permits a lower temperature fit and yields an upper limit of
$\Delta_{min} (0)/T_c = 0.2$.
