The Collaborative International Dictionary of English v.0.48:

Lernean \Ler*ne"an\ (l[~e]r*n[=e]"an), n. [See Lern[ae]a.]
   (Zool.)
   One of a family (Lern[ae]id[ae]) of parasitic Crustacea
   found attached to fishes and other marine animals. Some
   species penetrate the skin and flesh with the elongated head,
   and feed on the viscera. See Illust. in Appendix.
   [1913 Webster] lerot