  We show that in the collision of two superfluid fermionic atomic clouds one
observes the formation of quantum shock waves as discontinuities in the number
density and collective flow velocity. Domain walls, which are topological
excitations of the superfluid order parameter, are also generated and exhibit
abrupt phase changes by $\pi$ and slower motion than the shock waves. The
domain walls are distinct from the gray soliton train or number density ripples
formed in the wake of the shock waves and observed in the collisions of
superfluid bosonic atomic clouds. Domain walls with opposite phase jumps appear
to collide elastically.
