Each of the larger islands between Luzon and Mindanao, except Samar and Bohol, is traversed longitudinally by a single mountain range with occasional spurs.
In Samar there are irregular masses of hills.
Squirrels are confined to the eastern chain of islands from Basilan to Samar and to the Palawan-Calamianes group. In the southern islands there is a tiny species, the size of a mouse.
Galeopithecus and Tarsius range from Basilan to Samar; the former occurs also in Bohol.
These genera usually have distinct representative species in Luzon, Samar and Leyte, Mindanao, and in some cases in Basilan also.
