About at the same time when we received Büttikofer’s red-haired specimens of Orang-oetan ¹) from Borneo, I procured two dark-colored specimens, a female and a young, with their skeletons, collected near Sintang (Central Borneo). As the dark-colored specimens have been looked upon by some naturalists as belonging to a different species, Simia morio, it is evident that 1 now reviewed our rather large material of the Bornean Orang-oetan: the Sumatran-specimens, being very badly represented in the collections, as they seem to be rare to be had in Sumatra, we may leave out of consideration at present.