DISTRIBUTION OF BIRDS IN TIME AND SPACE. 197 



mainland — Australia — before the advent of even 

 the low mammalian types which characterise this 

 continent. The birds, reptiles, and flora of the 

 island are such as occur in Australia and the 

 adjacent Pacific Islands, and suggest an origin 

 from these sources. They are a part of a fauna 

 and flora once forming a common area. It is 

 supposed, however, that the island has been 

 isolated since the Cretaceous period. 



Soundings show that the "sea which directly 

 separates New Zealand from Australia is more 

 than 2000 fathoms deep, but in a north-west 

 direction there is an extensive bank under 1000 

 fathoms, extending to, and including. Lord Howe's 

 Island; while north of this are other banks of the 

 same depth, approaching towards a sub-marine 

 extension of Queensland on the one hand, and 

 New Caledonia on the other, and altogether sug- 

 gestive of a land union with Australia at some 

 very remote period." This suggested connection 

 is made almost a certainty by the evidence con- 

 tributed by the animal and plant life. The great 

 depth of the sea, as in the case between Africa 

 and Madagascar, together with the peculiarities 

 of the fauna in each case, furnish then strong 

 evidence that the period of isolation has, in 

 each case, been one of great length. 



We have one more instance of the significance 

 of a deep sea between two adjacent land areas. 

 This is furnished by the Malay Archipelago. A 

 line drawn between the two islands of Bali and 

 Lombok divides the Archipelago into two dis- 

 tinct zoo-geographical regions. The islands to 

 the west of this line belong to the Indian region, 



