Planorbis
Pronunciation : Pla*nor"bis
Part of Speech : n.
Etymology : [NL., fr. L. planus flat + orbis a circle.] (Zo?l.)
Definition : Defn: Any fresh-water air-breathing mollusk belonging to Planorbis and other allied genera, having shells of a discoidal form.
Source : Webster's Unabridged Dictionary, 1913