ON CORAL AND CORAL REEFS 135 



in which some of the most puzzling facts connected 

 with the distribution of animals have been brought 

 about. For example, Australia and New Guinea are 

 separated by Torres Straits, a broad belt of sea one 

 hundred or one hundred and twenty miles wide. Nev- 

 ertheless, there is in many respects -a curious resem- 

 blance between the land animals which inhabit New 

 Guinea and the land animals which inhabit Australia. 

 But, at the same time, the marine shellfish which are 

 found in the shallow waters of the shores of New 

 Guinea are quite different from those which are met 

 with upon the coasts of Australia. Now, the eastern 

 end of Torres Straits is full of atolls, which, in fact, 

 form the northern termination of the Great Barrier 

 Reef which skirts the eastern coast of Australia. It 

 follows, therefore, that the eastern end of Torres 

 Straits is an area of depression, and it is very possible, 

 and on many grounds highly probable, that, in former 

 times, Australia and New Guinea were directly con- 

 nected together, and that Torres Straits did not exist. 

 If this were the case, the existence of cassowaries and of 

 marsupial quadrupeds, both in New Guinea and in 

 Australia, becomes intelligible; while the difference 

 between the littoral molluscs of the north and the 

 south shores of Torres Straits is readily explained by 

 the great probability that, when the depression in 

 question took place, and what was, at first, an arm of 

 the sea became converted into a strait separating Aus- 

 tralia from New Guinea, the northern shore of this 

 new sea became tenanted with marine animals from 

 the north, while the southern shore was peopled by 

 immigrants from the already existing marine Australian 

 fauna. 



Inasmuch as the growth of the reef depends upon 



