Patagium (noun): a membrane or fold of skin between the forelimbs and hind limbs on each side of a bat or gliding mammal. Ornithologists also occasionally use it to refer to the forward part of bird wings. The word patagium is from Latin in which it refers to gold edging or a border on a woman's tunic.
In High Park, you may see the patagia (plural of patagium) of several species of bats. Until the mid-1970's flying squirrels were also present in High Park, gliding from the tree tops with their patagia outstretched.