The supermoduli space of matrix string theory

We study matrix string scattering amplitudes and matrix string instantons o n a marked Riemann surface in the limit of a vanishing string coupling cons tant. We give an explicit parameterization of the moduli space of such inst antons. We also give a description of the set of fermionic supermoduli. The integration over the supermoduli leads to the inclusion of picture changin g operators at the interaction points. Finally we investigate the large-N l imit of the measure on the instanton moduli space and show its convergence to the Weil-Petersson measure on the moduli space of marked Riemann surface s.