Hydrachnid
Pronunciation : Hy*drach"nid
Part of Speech : n.
Etymology : [Hydr- + arachnid.] (Zo?l.)
Definition : Defn: An aquatic mite of the genus Hydrachna. The hydrachids, while young, are parasitic on fresh-water mussels.
Source : Webster's Unabridged Dictionary, 1913