  We describe explicitly all hyperelliptic limits of quadrics through smooth
canonical curves of genus $g$ in ${\mathbb P}^{g-1}$. Also, we construct an
open embedding of the blow up of a ${\rm PGL}_g$-bundle over the moduli space
of curves of genus $g$ along the hyperelliptic locus into the blow up of the
canonical Hilbert scheme of ${\mathbb P}^{g-1}$ along the closure of the locus
of canonical ribbons, which are certain double thickenings of rational normal
curves introduced and studied by Bayer and Eisenbud.
