  New universality appears for the baryon Isgur--Wise form factor in the large
$N_c$ limit. It is found that the semileptonic $\Lambda_b \rightarrow
\Lambda_c$ and $\Sigma_b^{(*)} \rightarrow \Sigma^{(*)}_c$ decays are described
by the same form factor, which can be calculated analytically. In the exact
chiral $SU(3)$ limit, the same form factor is applicable to semileptonic
$\Omega_b^{(*)} \rightarrow \Omega^{(*)}_c$ decays.
