  Riley "defined" the Heckoid groups for 2-bridge links as Kleinian groups,
with nontrivial torsion, generated by two parabolic transformations, and he
constructed an infinite family of epimorphisms from 2-bridge link groups onto
Heckoid groups. In this paper, we make Riley's definition explicit, and give a
systematic construction of epimorphisms from 2-bridge link groups onto Heckoid
groups, generalizing Riley's construction.
