  We present specific heat measurements which show an unexpected phase
transition from d-wave symmetry to s-wave symmetry as the temperature is
reduced in electron-doped Pr$_{2-x}$Ce$_{x}$CuO$_{4-\delta}$ (PCCO), in both
optimal and over-doped single crystals. The field dependence of electronic
specific heat (C$_{el}$) is linear at T=2K, consistent with s-wave symmetry,
and non-linear, consistent with d-wave symmetry, at T$\geq$3K. This behavior is
most consistent with a phase transition in the symmetry of the order parameter
as the temperature is changed. Such a phase transition could be an explanation
for the previous controversial results of different experiments, performed at
different temperatures in the electron-doped cuprates.
