102 BULLETIN: MUSEUM OF COMPARATIVE ZOOLOGY. 



the inner reef patches leaving only a narrow channel close to the main- 

 land. The reef then turns north again, extending parallel to the coast 

 line as far as Cape Grenville, at a distance varying between fifteen and 

 thirty miles, but as the coast approaches that cape it trends somewhat 

 more easterly, the outer edge of the reef gradually becoming more dis- 

 tant from the coast, until at the latitude of Cape York it has attained a 

 width of over eighty miles, and forms a huge plateau within the 

 twenty fathom line, irregularly studded with reef patches which connect 

 New Guinea with the Australian continent. To the westward of Eagle 

 Reef, En Island and the Turtle group are the only islands between the 

 inner reef patches and the mainland. 



An examination of the charts (Plates XXIV., XXXV., XXXVI.) shows 

 that the northern part of the Great Barrier Reef presents as far as it has 

 been surveyed no features differing from those of the southern district 

 which it has been our fortune to examine. Everywhere a series of isl- 

 ands rising upon the continental plateau scattered between the main- 

 land and its outer edge, with irregular patches of reef fiats and reefs, 

 growing upon the remnants of former islands which have been reduced 

 to their present level by erosion and denudation, all apparently hav- 

 ing formerly formed a part of the eastern extension of the Australian 

 continent. 



The Great Detached Reef and Yule Reef alone are exceptions to this. 

 When we come to the region about Cape York we have exemplified in the 

 stretch extending between Australia and New Guinea the conditions 

 which once existed between the east coast of Queensland and the outer 

 edge of the Great Bai'rier Reef. The group of islands to the west of 

 Cape York, extending nearly across to New Guinea from Prince of Wales 

 to Jervis Island, the northern gi-oup of which is separated from the 

 southern cluster by extensive reefs and reef patches, give us an admirable 

 idea of the manner in which the islands have little by little been first 

 separated by erosion from the mainland, denuded, and cut down many 

 of them to the water's edge, then pounded into flats, and finally their 

 slopes covered with corals. While the line of islands and reefs extend- 

 ing in a northeasterly direction from Cape York, the group of the Adol- 

 phus Islands, and the series of reef patches extending almost continuously 

 as far as the Warrior Reefs, are the remnant of a series of outer islands 

 which have all, except those nearest Cape York, (the Adolphus and 

 Albany Islands, and the Darnley and Murray Islands to the east,) 

 been subject for a longer time to the same processes which have 

 gradually cut away the land connection between Australia and New 



