Patagium:

* In bats, the skin forming the surface of the wing. It is an extension of the skin of the abdomen that runs to the tip of each digit, uniting the forelimb with the body.

* In gliding species, such as some lizards, rodents, and primates, the flat parachute-like extension of skin that catches the air, allowing them to glide.

* In some lepidopterans, one of a pair of small sensory organs situated at the bases of the anterior wings.

* In birds, the fold of skin extending from the humerus to the carpal joint, making up the leading edge of the wing.

http://en.wikipedia.org/wiki/Patagium