  We perform Monte Carlo simulations to determine the average excluded volume
<V_{ex}> of randomly oriented rectangular prisms, randomly oriented ellipsoids
and randomly oriented capped cylinders in 3-D. There is agreement between the
analytically obtained <V_{ex}> and the results of simulations for randomly
oriented ellipsoids and randomly oriented capped cylinders. However, we find
that the <V_{ex}> for randomly oriented prisms obtained from the simulations
differs from the analytically obtained results. In particular, for cubes, the
percentage difference is 3.92, far exceeding the bounds of statistical error in
our simulation.{\bf Added in Revision 2: We recently found the cause of the
discrepancy between the simulation result and the analytic value of the
excluded volume to be the effect of an error in our simulation code. Upon
rectification of the simulation code, the simulation yields $ 11.00 \pm 0.002 $
as the excluded volume of a pair of randomly oriented cubes of unit volume. The
simulation also yields results as predicted by the analytic formula for all
other cases of rectangular prisms that we study.}
