  We present a Spitzer based census of the IC 348 nebula and embedded star
cluster. Our Spitzer census supplemented by ground based spectra has added 42
class II T-Tauri sources to the cluster membership and identified ~20 class 0/I
protostars. The population of IC 348 likely exceeds 400 sources after
accounting statistically for unidentified diskless members. Our Spitzer census
of IC 348 reveals a population of protostars that is anti-correlated spatially
with the T-Tauri members, which comprise the centrally condensed cluster around
a B star. The protostars are instead found mostly at the cluster periphery
about 1 pc from the B star and spread out along a filamentary ridge. We find
that the star formation rate in this protostellar ridge is consistent with that
rate which built the exposed cluster while the presence of fifteen cold,
starless, millimeter cores intermingled with this protostellar population
indicates that the IC 348 nebula has yet to finish forming stars. We show that
the IC 348 cluster is of order 3-5 crossing times old, and, as evidenced by its
smooth radial profile and confirmed mass segregation, is likely relaxed. While
it seems apparent that the current cluster configuration is the result of
dynamical evolution and its primordial structure has been erased, our findings
support a model where embedded clusters are built up from numerous smaller
sub-clusters. Finally, the results of our Spitzer census indicate that the
supposition that star formation must progress rapidly in a dark cloud should
not preclude these observations that show it can be relatively long lived.
