  We discuss the problem of classifying birational extremal contractions of
smooth threefolds where the canonical bundle is trivial along the curves
contracted, in the case when a divisor is contracted to a point. We prove the
analytic rigidity of the contraction in the case this divisor is normal of
degree >= 5 (i.e. we show that the analytic structure of the contraction is
completely determined by the isomorphism class of the exceptional locus and its
normal bundle in X). This was previously known only in the case of smooth
exceptional locus.
