The Collaborative International Dictionary of English v.0.48:

Annelid \An`ne*lid\, Annelidan \An*nel"i*dan\, a. [F.
   ann['e]lide, fr. anneler to arrange in rings, OF. anel a
   ring, fr. L. anellus a ring, dim. of annulus a ring.] (Zool.)
   Of or pertaining to the Annelida. -- n. One of the Annelida.
   [1913 Webster]

WordNet (r) 3.0 (2006):

annelidan
    adj 1: relating to or belonging to or characteristic of any
           worms of the phylum Annelida [syn: annelid,
           annelidan]