third eyelid n a protective fold of skin in the eyes of reptiles and birds and some mammals Synonym(s) nictitating membrane
News & Articles third eyelid Otters are made for swimming River otters can hold their breath for about eight minutes, and they have a special third eyelid that allows them to keep their eyes open underwater. / Special to WNC Parent June 13, 2013 - Asheville Citizen-Times