112 bulletin: museum of comparative zoology. 



rated, which lead towards the 100 fathom line, and form a uniformly 

 sloping channel from the inner reef channel to the sea. There being no 

 outer Barrier Reef patches, or outer reef channel, as along other parts of 

 the reef (as south of Lark Pass, for instance, and elsewhere), where 

 the outer Barrier Reef forms a series of linear or curved reefs, separated 

 from the inner reef patches by a channel of from twelve to tweuty fath- 

 oms in depth. With the exception of the few insignificant reef patches 

 scattered across the middle of Trinity Opening, that channel is flanked 

 on the north by Butt Reef and on the south by Oyster Reef, both of 

 which are reef patches forming the eastern flank of the inner Barrier 

 Reef channel (Plate XXXI. ). 



Before going on with the description of the inner and outer reef 

 patches, it may be well to give that of the smaller island groups north 

 of Trinity Opening as far as the Lizards, mauy of which are gradually 

 changing into reef flats. 



Continuing our examination of the islands situated between the inner 

 western edge of the Barrier Reef and the mainland, we come north of 

 Trinity Opening, first upon the Low Isles situated in midchannel. Close 

 to the mainland is Snapper Islaud. About thirty-five miles north of the 

 Low Isles we come upon the Hope Islands (Plate XXXIL). 



The smaller of the Hope Islands to the east is a sandy islaud flanked 

 on the southeast by an immense flat covered by dead coral (Plate VI.), 

 and numerous fragments of beach rock, forming an irregular pavement. 

 The fauna living under these stones is quite rich, and between them 

 were found numerous huge Actinise, Alcyonarians, Zoanthus, and Annel- 

 lids, as well as an occasional living coral. On the coral reef flat there 

 were found many Tridacnas, Holothurians, long-armed Ophiurans, huge 

 Synaptas, and splendidly colored Macrurans and Brachiurans. 



On the slope to the leeward of the flat were growing fine patches of 

 corals, with sponges, Actinians, Alcyonarians, Fuugidae, Millepores, huge 

 masses of Pocillopora, Madrepores, heads of Astrseans, of Gymnastrae- 

 ans, and of Maeandrinas. These heads and patches begin to make their 

 appearance in from six to seven fathoms, increasing gradually in num- 

 ber and species to between five and three fathoms of water, where they 



land rivers, like the Burnett, Fitzroy, and others. If there has been a subsidence 

 of about 100 feet, as indicated by the river beds near Townsville, it is very proba- 

 ble that the course of the Queensland rivers extended farther out to the edge of 

 the Great Barrier Reef, and that some of the breaks and passages extending west- 

 ward may have been originally due to the action of the rivers, an influence at this 

 day reaching only a comparatively short distance from the shores of the mainland. 





