Source : Webster's Revised Unabridged Dictionary (1913)

Hypoarion \Hy`po*a"ri*on\, n.; pl. {Hypoaria}. [NL., fr. Gr.
   "ypo` beneath + ? a little egg.] (Anat.)
   An oval lobe beneath each of the optic lobes in many fishes;
   one of the inferior lobes. --Owen.