What is "abranchiata"

Abranchiata \A*bran`chi*a"ta\, n. pl. [NL., from Gr. 'a priv. + ?, pl., the gills of fishes.] (Zo["o]l.) A group of annelids, so called because the species composing it have no special organs of respiration.

n. 1 (context zoology English) An obsolete order of annelids, so called because the species composing it have no special organs of respiration. 2 Any of a number of gill-less animals excluding Abranchia.