112 MOSTLY MAMMALS 
and feeding at night. If these creatures were of a type 
near to that from which the other marsupials of Australia 
have sprung, they might be considered as survivors from 
a migration of marsupials which it has been suggested 
took place at a remote epoch from Asia to Australia. But 
they are not so, and it is therefore clear that this hypo- 
thesis will not account for their presence in the island. 
As they are so completely arboreal in their habits, they 
are, however, just the kind of creatures which we might 
naturally expect to be wafted from one island to another on 
floating timber; and it is far from improbable that it is to 
this mode of transport they owe their presence in Celebes. 
All the other mammals are of an Oriental type, although 
several of them are quite unlike their relatives on the 
mainland and other islands. Among them one of the 
most remarkable is the babirusa, a curious little pig in 
which the tusks of both jaws in the males attain a most 
extraordinary development, the lower ones rising straight 
upwards, while the upper ones grow right through the 
skull to curve backwards in a bold sweep towards the 
eyes. Although nothing definitely is known as to the 
origin of this strange animal, yet it is evidently a highly 
specialised offshoot from the ancestral pigs of Asia, Equally 
peculiar is the tiny little black buffalo, or anoa, described 
in another article, which is not much larger than a good- 
sized ram, and has upright horns quite unlike those of the 
ordinary Asiatic buffalo. In the island of Mindanao, the 
most southern of the Philippine group, there is, however, 
a considerably larger buffalo, known as the tamarao, which 
serves to connect the anoa with the ordinary Asiatic species. 
More important still is the occurrence in the Tertiary 
deposits of Northern India of several species of buffaloes 
intimately related to the anoa. Clearly, then, this animal 
