membrana nictitans

pli·ca sem·i·lu·na·'ris of con·junc·ti·'va

[TA]
1. the semilunar fold formed by the palpebral conjunctiva at the medial angle of the eye;
2. a fold of the conjunctival mucous membrane found in many animals; normally partially hidden in the medial canthus of the eye when at rest, it may be extended to cover part or all of the cornea in a winklike action to clean the cornea, as in birds. Synonym(s): membrana nictitans, nictitating membrane, palpebra III, palpebra tertia, third eyelid

membrana nictitans

(1) Semilunar fold of conjunctiva; plica semilunaris conjunctivae [NA6]. 
(2) Nictitating membrane.
References in periodicals archive ?
The dogs treated by anchoring of gland to periosteum of orbital rim also had excellent cosmetic appearance and did not recur during the follow up period, however, membrana nictitans got fixed, covering medial 1/4 (th) of cornea, restricting its movement (Fig.
In cattle, it usually involves cornea and conjunctiva but sometimes membrana nictitans and eyelids also (Tyagi and Singh, 1993).