Archiannelida \Ar`chi*an*nel"i*da\, n. pl. [NL.; pref. archi- + annelida.] (Zo["o]l.) A group of Annelida remarkable for having no external segments or distinct ventral nerve ganglions.
Archiannelida n : a class of Annelida [syn: {class Archiannelida}]