  The authors study the geometry of lightlike hypersurfaces on a
four-dimensional manifold $(M, c)$ endowed with a pseudoconformal structure $c
= CO (2, 2)$. They prove that a lightlike hypersurface $V \subset (M, c)$ bears
a foliation formed by conformally invariant isotropic geodesics and two
isotropic distributions tangent to these geodesics, and that these two
distributions are integrable if and only if $V$ is totally umbilical. The
authors also indicate how, using singular points and singular submanifolds of a
lightlike hypersurface $V \subset (M, c)$, to construct an invariant
normalization of $V$ intrinsically connected with $V$.
