What does annelid or annelidan mean?
The definition of annelid and annelidan
An`ne*lid, An*nel”i*dan, a.
Etym: [F. annélide, fr. anneler to arrange in rings, OF. anel a ring, fr. L. anellus a ring, dim. of annulus a ring.] (Zoöl.)

Of or pertaining to the Annelida.

— n.

One of the Annelida.