  The spectrum of excited $\Lambda_Q$-type heavy baryons is considered in the
large $N_c$ limit. The universal form factors for $\Lambda_b$ semileptonic
decay to excited charmed baryons are calculated in the large $N_c$ limit. We
find that the Bjorken sum rule (for the slope of the Isgur--Wise function) and
Voloshin sum rule (for the mass of the light degrees of freedom) are saturated
by the first doublet of excited $\Lambda_Q$ states.
