Having thus briefly indicated those physical features of Borneo which are necessary for our inquiry, let us turn to the organic world. Neither as regards this great island nor those which surround it, have we the amount of detailed information in a convenient form that is required for a full elucidation of its past history. We have, however, a tolerable acquaintance with the two higher groups--mammalia and birds, both of Borneo and of all the surrounding countries, and to these alone will it be necessary to refer in any detail. The most convenient course, and that which will make the subject easiest for the reader, will be to give, first, a connected sketch of what is known of the zoology of Borneo itself, with the main conclusions to which they point; and then to discuss the mutual relations of some of {376} the adjacent islands, and the series of geographical changes that seem required to explain them. ZOOLOGICAL FEATURES OF BORNEO. _Mammalia._--Nearly a hundred and forty species of mammalia have been discovered in Borneo, and of these more than three-fourths are identical with those of the surrounding countries, and more than one half with those of the continent. Among these are two lemurs, nine civets, five cats, five deer, the tapir, the elephant, the rhinoceros, and many squirrels, an assemblage which could certainly only have reached the country by land. The following species of mammalia are supposed to be peculiar to Borneo:-- QUADRUMANA. 1. Simia morio. A small orangutan with large incisor teeth. 2. Hylobates mulleri. 3. Nasalis larvatus. 4. Semnopithecus rubicundus. 5. " chrysomelas. 6. " frontatus. 7. " hosei. (Thomas.) Kini Balu. CARNIVORA. 8. Herpestes semitorquatus. 9. Felis badia. UNGULATA. 10. Sus barbatus. RODENTIA. 11. Pteromys phaeomelas. 12. Sciurus jentinki. (Th.) Kini Balu. 13. Sciurus whiteheadi. (Th.) Kini Balu. 14. " everetti. 15. Rheithrosciurus macrotis. 16. Hystrix crassispinis. 17. Trichys guentheri. 18. Mus infraluteus. (Th.) Kini Balu. 19. " alticola. (Th.) Kini Balu. INSECTIVORA. 20. Tupaia splendidula. 21. " minor. 22. " dorsalis. 23. Dendrogale murina. CHIROPTERA. 24. Vesperugo stenopterus. 25. " doriae 26. Cynopterus brachyotus. 27. " lucasii. 28. " spadiceus. 29. Hipposideros doriae.