The plica semilunaris is the vestigial remains of the nictitating membrane (or 'third eyelid') found in many fish, birds, and a few mammals. The plica semilunaris and its connected muscles serve no current function, but certainly did in human ancestral species, protecting the eye from foreign contaminants.

yes boss it is :)

It is often called a third eyelid or haw (and may be referred to as the plica semilunaris or palpebra tertiain scientific terminology).

The plica (PLY-ka) semilunaris (sem-ee-LOO-ner-is), which is located around the eye was thought to have no function. But eventually it was discovered that this "useless" organ has an important function after all.

In fact, it is the "crusty" factory. It secretes a sticky mass that collects any foreign materials such as dust or pollen. All this trash is surrounded by the sticky gook so that it does not scratch the sensitive cornea in your eye. Once the garbage is collected, the plica semilunaris "escorts" it out of the eye just like a security guard would escort noisy troublemakers out of a theater.

Julian Plica was born in 1978, in Munich, Bavaria, Germany.