  We show that except for one exceptional case, a lamination on the boundary of
a 3-dimensional handlebody H is a Hausdorff limit of meridians if and only if
it is commensurable to a lamination with a 'homoclinic leaf'. This is a precise
version of a philosophy called Casson's Criterion, which appeared in
unpublished notes of A. Casson. Applications include a characterization of when
a non-minimal lamination is a Hausdorff limit of meridians, in terms of
properties of its minimal components, and a related characterization of which
reducible self-homeomorphisms of the boundary of H have powers that extend to
subcompressionbodies of H.
