  We consider a simplicial complex generaliztion of a result of Billera and
Meyers that every nonshellable poset contains the smallest nonshellable poset
as an induced subposet. We prove that every nonshellable $2$-dimensional
simplicial complex contains a nonshellable induced subcomplex with less than
$8$ vertices. We also establish CL-shellability of interval orders and as a
consequence obtain a formula for the Betti numbers of any interval order.
