  Recently, a non-hyperelliptic curve describing the Coulomb branch of N=2 SUSY
$SU(N_c)$ Yang-Mills theory with an antisymmetric tensor matter was proposed
using a configuration of a single M theory five-brane. We study the singular
surface in the moduli space of the curve to compare it with results from the
``integrating in'' method in field theory. In order to achieve the consistency,
we find it necessary to take account of an additional superpotential
$W_{\Delta}$ which has been neglected so far. The explicit form of $W_{\Delta}$
is worked out.
