New Universality of Baryon Isgur--Wise Form Factor in the Large $N_c$ limit

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.