154 Natural History of the 



families as the woodpeckers, parrots, trogons, barbets, king- 

 fishers, pigeons, and pheasants, we find some identical species 

 spreading over all India, and as far as Java and Borneo, 

 while a very large proportion are common to Sumatra and 

 the Malay Peninsula. 



The force of these facts can only be appreciated when we 

 come to treat of the islands of the Austro-Malay region, and 

 show how similar barriers have entirely prevented the pas- 

 sage of birds from one island to another, so that out of at 

 least three hundred and fifty land birds inhabiting Java and 

 Borneo, not more than ten have passed eastward into Celebes. 

 Yet the Straits of Macassar are not nearly so wide as the Java 

 sea, and at least a hundred species are common to Borneo 

 and Java. 



I will now give two examples to show how a knowledge 

 of the distribution of animals may reveal unsuspected facts 

 in the past history of the earth. At the eastern extremity 

 of Sumatra, and separated from it by a strait about fifteen 

 miles wide, is the small rocky island of Banca, celebrated for 

 its tin-mines. One of the Dutch residents there sent some 

 collections of birds and animals to Leyden, and among them 

 were found several siDecies distinct from those of the adjacent 

 coast of Sumatra. One of these was a squirrel (Sciurus 

 bangkanus), closely allied to three other species inhabiting 

 respectively the Malay Peninsula, Sumatra, and Borneo, but 

 quite as distinct from them all as they are from each other. 

 There were also two new ground-thrushes of the genus Pitta, 

 closely allied to, but quite distinct from, two other species in- 

 habiting both Sumatra and Borneo, and which did not per- 

 ceptibly differ in these large and widely-separate islands. 

 This is just as if the Isle of Man possessed a peculiar species 

 of thrush and blackbird distinct from the birds which are 

 common to England and Ireland. 



These curious facts would indicate that Banca may have 

 existed as a distinct island even longer than Sumatra and 

 Borneo, and there are some geological and geographical facts 

 which render this not so improbable as it would at first seem 

 to be. Although on the map Banca appears so close to 

 Sumatra, this does not arise from its having been recently 

 separated from it ; for the adjacent district of Palembang is 



