12 NILS GYLDENSTOLPE, ZOOLOGICAL RESULTS OF THE SWEDISH ZOOLOGICAL EXPEDITIONS TO SIAM. 
soon followed which destroyed the connection between Sumatra and the Malay Penin- 
sula. Ceylon, which at the present time exhibits a Fauna which in several ways differs 
from that one of the upper parts of the Indian Peninsula, had already been separated 
probably at about the same time as Borneo. As a completion to the development it 
seems as if the Bengal Sea is regressing, so that an exchange between the Fauna of the 
Indian Peninsula and that one of the Malay Peninsula was made possible. 
On the Malay Peninsula the Malayan elements are predominant. This is especially 
evident concerning the Mammalian Fauna which highly resembles that one of Sumatra. 
There are, however, also several species which have had their origin in India and which 
have migrated to the Malay Peninsula since the connection with Sumatra already was 
destroyed. 
Towards the north the Malayan Fauna extends as far as Pegu. Southern Siam and 
Tenasserim constitute, however, territories in which the Fauna is of a decidedly mixed 
origin. The Eastern parts of Further India, through which sinic mountain chains are 
running, has a very peculiar Fauna, the chief character of which is the total absence of 
several pure Malayan forms. These forms, however, occur again on the lower slopes of 
the Himalayas and in Southern China. Further India and especially the Eastern parts 
of the same are therefore to be considered as very important for the development of the 
present Fauna which still continues. These parts then most probably constituted one 
of the centres of distribution for the Malayan Fauna. Borneo and Sumatra seems to 
have constituted another centre. These two centres were probably in connection with 
each other though the connection was destroyed before the development was actually 
completed. 
In course of time the Fauna of Further India spread out in every direction. 
Southern China and Northern Siam are traversed by mountain chains running 
in a northern-southern direction and the numerous valleys formed excellent routes for 
the further distribution of the animals. Both Hainan and Formosa were at that time 
united with the Chinese continent and on account of this these islands possess a Fauna 
which in several respects still reminds of that of the mainland.’ Even the Fauna of the 
Indian Peninsula is strongly represented im Further India. 
From a Zoogeographical point of view I therefore divide Siam into three different 
regions: 1) the mountain region of Northern Siam, 2) the lowlands of Northern and 
Central Siam and 3) Lower Siam. 
When looking at the Fauna in the mountain regions of Northern Siam one of the 
most striking facts is the near affinity to the Fauna of the Himalayas, and several forms 
characteristic to the Himalayas have also been found in Siam. The mountains of the 
Malay Peninsula which like a backbone are running down the whole Peninsula are 
showing the same affinity though the Malayan forms predominate the further south 
we reach. The mountains of the Malay Peninsula and those of Sumatra, Borneo, Java, 
Hainan, Formosa and the Philippines are displaying a similar character though they 
sometimes differ inter se on account of the different time at which these islands got sep- 
1 Vide: Kungl. Svenska Vetenskapsakademiens Handlingar. Bd. 50. N:o 8 1913. 
