Source : Webster's Revised Unabridged Dictionary (1913)

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.

Source : WordNet®

Archiannelida
     n : a class of Annelida [syn: {class Archiannelida}]