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 flats 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 Barrier Reef. "The group of islands to the west of 
Cape York, extonding nearly across to New Guinea from Prince of Wales 
to Jervis Island, the northern group of which is separatod 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 
