from
The Collaborative International Dictionary of English v.0.48
Flying squirrel \Fly"ing squir"rel\ (? or ?). (Zool.)
One of a group of squirrels, of the genus {Glaucomys}
(formerly {Pteromus} and {Sciuropterus} [1913 Webster]),
especially {Glaucomys volans} and {Glaucomys sabrinus},
having parachute-like folds of skin extending from the fore
to the hind legs, which enable them to make very long,
gliding leaps.
[1913 Webster +PJC]
Note: The species of Pteromys are large, with bushy tails,
and inhabit southern Asia and the East Indies; those of
Sciuropterus are smaller, with flat tails, and inhabit
the northern parts of Europe, Asia, and America. The
American species {(Sciuropterus volucella)} is also
called Assapan. The Australian flying squirrels, or
flying phalangers, are marsupials. See {Flying
phalanger} (above).
[1913 Webster]