Source : Webster's Revised Unabridged Dictionary (1913)

Helicotrema \Hel`i*co"tre"ma\, n. [NL., fr. Gr. "e`lix, -ikos, a
   helix + ? a hole.] (Anat.)
   The opening by which the two scal[ae] communicate at the top
   of the cochlea of the ear.