The Collaborative International Dictionary of English v.0.48:

Archetypical \Ar`che*typ"ic*al\, a.
   Relating to an archetype; archetypal.
   [1913 Webster]

WordNet (r) 3.0 (2006):

archetypical
    adj 1: representing or constituting an original type after which
           other similar things are patterned; "archetypal
           patterns"; "she was the prototypal student activist"
           [syn: archetypal, archetypical, prototypal,
           prototypic, prototypical]