chætonotus

from The Century Dictionary.

• noun A genus of minute aquatic worm-like animals of uncertain position, referred by Ehrenberg to the rotifers, by Dujardin to the infusorians; and they are placed by some writers with Ichthyidium in the order of oligochætous annelids, and by others with Ichthyidium and some related genera in a separate class Gastrotricha.