The Collaborative International Dictionary of English v.0.48:

Prefatory \Pref"a*to*ry\, a.
   Pertaining to, or of the nature of, a preface; introductory
   to a book, essay, or discourse; as, prefatory remarks.
   [1913 Webster]

         That prefatory addition to the Creed.    --Dryden.
   [1913 Webster]

WordNet (r) 3.0 (2006):

prefatory
    adj 1: serving as an introduction or preface [syn:
           introductory, prefatorial, prefatory]