Webster’s Revised Unabridged Dictionary · 1913
Hypoarion
Hy′po·a′ri·on (·ŏn), n.; pl. Hypoaria (#). [NL., fr. Gr. ὑπό beneath + ᾠάριον a little egg.] (Anat.) An oval lobe beneath each of the optic lobes in many fishes; one of the inferior lobes. Owen.