  Lejeune-Jalabert showed that the fundamental class of a Cohen-Macaulay ideal
$\mathfrak a\subset \mathcal O_0$ admits a representation as a residue,
constructed from a free resolution of $\mathfrak a$, multiplied by a certain
differential form coming from the resolution. We give an explicit description
of this differential form in the case where the free resolution is the Scarf
resolution of a generic monomial ideal. As a consequence we get a new proof and
a refinement of Lejeune-Jalabert's result in this case.
