THE AUSTRALIAN GREAT BARRIER REEF. 121 



so universally useful a mission as was originally anticipated. The intricacies of the navigation 

 among the reefs, between the passage and the open channel near the mainland, occasioned so many 

 wrecks and misadventures that the route was finally abandoned, by all but small craft, in favour 

 of the much more open, although more remote, one known as the Great North-East or Blyth 

 Channel, adjacent to the coast of New Guinea. 



The comparatively short distance (a little over eighty nautical miles) between the parallels 

 of Raine Island and Cape Grenville, and Cape York and Torres Strait, presents no special 

 features, with the exception that the outer edge of the Barrier (following a course almost due 

 north, and ultimately north-east, the trend of the land being north-west by north), while 

 within forty miles of the coast abreast of Cape Grenville, is eighty miles from it opposite 

 Cape York, the most northern point of Queensland, or, indeed, of the Australian Continent. 

 The greater part of this area, exterior to the navigable coastal channel, is one intricate 

 maze of coral-reefs, islets, and shoals, to a large extent unexplored, and marked on the 

 Admiralty charts as "dangerous navigation." At several stages along the charted navigable 

 route, north of Cape Melville, the steamers making for or hailing from Torres Strait are 

 accustomed, unless it is particularly clear, to anchor for the night. The Cairn Cross Islands, 

 a little coral group midway between Cape Grenville and Cape York, is one of these commonly 

 chosen anchoring stations ; and, if arrived at an hour or two before dusk, the opportunity of 

 a brief run ashore is frequently afforded passengers. Such an opportunity occurred, and was 

 utilised by the author, when on a voyage from Sydney to Port Darwin, by one of the China 

 Navigation Company's ships, in the year 1888, and represented, in point of fact, his first practical 

 acquaintance with a coral reef On this occasion only a portion of the inshore, or upper, platform 

 reef was uncovered by the tide ; but to one to whom such a scene was entirely new the experience 

 was absorbingly interesting. In the shallow pools or thin sheets of water just covering the reef, 

 black Beche-de-mer, Holotliuria alra, and H. coluber, were extended in every direction, grasping 

 sand and coral particles with their extended tentacles, which, being withdrawn, food-laden, 

 were thrust, one after the other, into the circular mouths. Other varieties of Holothuria were 

 found concealed under the broken slabs of reef-rock ; and from the same coign of vantage might be 

 seen protruding on every side the long spinous arms of a brittle starfish, apparently identical with 

 Opiiioiiiastix aiumlosa, represented by Chromo plate XL, Fig. 11. The arms of the starfish, which 

 are five, are exceedingly flexible. Numerous extensive membranous suckers are developed 

 from their central groove ; and they thus constitute very efficient prehensile organs, which 

 extend in a tentative manner in all directions, while the body remains concealed, and seize and 

 convey to the mouth any suitable substances. The same shallow pools on the Cairn Cross 

 reefs were thickly tenanted by a delicate, transparent, pink Synapta, from six to eight or ten 

 inches long, when expanded, which were extended, and feeding in the same manner as the 

 larger Holothuriae. Chromo plate XII., Fig. 9, represents a group of Synaptse of very similar 



