Assertion: beaver's eyelid | /r/Synonym | nictitating membrane
Facets:
Source sentences:
text: Beavers also have a third, transparent eyelid (called a nictitating membrane) that protects their eyes as they swim underwater.
text: The ears and nose are equipped with valve-like flaps that can be closed underwater, while the small eyes have a protective transparent eyelid (nictitating membrane).
text: Their eyes are protected by a third eyelid called a nictitating membrane.