  In this paper, we present, given a odd integer $d$, a decomposition of the
multiset of bar lengths of a bar partition $\lambda$ as the union of two
multisets, one consisting of the bar lengths in its $\bar{d}$-core partition
$\bar{c}_d(\lambda)$ and the other consisting of modified bar lengths in its
$\bar{d}$-quotient partition. In particular, we obtain that the multiset of bar
lengths in $\bar{c}_d(\lambda)$ is a sub-multiset of the multiset of bar
lengths in $\lambda$. Also we obtain a relative bar formula for the degrees of
spin characters of the Schur extensions of the symmetric group. The proof
involves a recent similar result for partitions, proved in [1].
