The Collaborative International Dictionary of English v.0.48:

Argulus \Ar"gu*lus\, n. [NL., dim of Argus.] (Zool.)
   A genus of copepod Crustacea, parasitic of fishes; a fish
   louse. See Branchiura.
   [1913 Webster]

The Collaborative International Dictionary of English v.0.48:

Branchiura \Bran"chi*u"ra\, n. pl. [NL., fr., Gr. ? gill +
   o'yra` tail.] (Zool.)
   A group of Entomostraca, with suctorial mouths, including
   species parasitic on fishes, as the carp lice (Argulus).
   [1913 Webster]