The Collaborative International Dictionary of English v.0.48:

Errantia \Er*ran"ti*a\, n. pl. [NL., fr. L. errare to wander.
   See Err.] (Zo["o]l.)
   A group of ch[ae]topod annelids, including those that are not
   confined to tubes. See Ch[ae]topoda. [Written also
   Errantes.]
   [1913 Webster]