According to this site there are two species of North American flying squirrel: northern flying squirrel Glaucomys sabrinus and the southern flying squirrel, Glaucomys volans. Their ranges are overlapping and, to complicate matters further, there are at least two sub-species of the northern, G. sabrinus coloratus, the Carolina northern and G. sabrinus fuscus, the Virginia northern. Pteromys sp. are the Old World flying squirrels.

Edit:

Kids these days want everthang. OK, here's the site:

http://www.isidore-of-seville.com/flyingsquirrel/

Mehbe they changed genus names on us. Quick's you learn the old one they got somebody ready to pull up a new one.