Up to this day I knew only a single Mammal, Sciurus prevostii, from Billiton, a small island, situated between Borneo and Banka. As the islands between Sumatra and Borneo bear a peculiar scientific interest with regard to the distribution of the animals and to the hypothesis concerning the relation in prehistorical times between these two large islands, I was in sanguine expectations in receiving a letter from Dr. A. Vorderman (Batavia), containing the kind information that he had made a journey to Billiton in June 1888 and now presented the then collected animals to our Museum. And how great was my astonishment in finding in that collection no less than 10 species of Mammals from Billiton. So that we know at present eleven well-defined species from that interesting point in the Malay Archipelago. Two species, Pteropus edulis and Sciurus prevostii ,in the collection are from Mendanao, a small island close to the west coast of Billiton.