44 THE GREAT BARRIER REEF. 



existence. In this respect their earhest or larval condition corresponds with the adult state 

 of the permanently stalked and sedentary Crinoids or Sea-lilies, most abundant in earlier geo- 

 logical epochs, but now represented by but a few comparatively rare abyssal forms. From 

 an evolutionary point of view, the roving Feather-stars are consequently regarded as the 

 direct descendants of the permanently stalked Lily-stars, with which, in all other essential 

 anaiomical features, they are found to correspond. 



PLATE XXIX. 



(A,)-OUTER BSRRIER REEF, WITH GIMT CLSMS ilND BECHE-DE-MER. 



This reef-scape is highly t3-pical of those vast areas of the Outer Barrier district from which 

 the richest harvests of Trepang or Beche-de-mer are systematically obtained. Examples of the 

 Beche-de-mer, outstretched at ease, may be discerned beneath the surface of the shallow, glass- 

 clear water that, at the lowest tide-ebb, still covers the most considerable area of the reef-surface. 

 The most conspicuous object in this illustration is undoubtedly, however, the huge mass in the 

 immediate foreground, which, excepting for its sinuous upper edge, might be readily mistaken 

 for an eroded coral-boulder. This represents, on its native reef, that most colossal of living 

 bivalve molluscs, the Giant Clam, Tridacna gigas. The specimen here figured measured just 

 three feet six inches in length, but it by no means illustrates the largest dimensions that may 

 obtain. A measurement of as much as four feet, with an associated weight, with the enclosed 

 living animal, of at least six or seven hundredweight, frequently occurs. The largest pair of 

 shells of this species displayed at the International Fisheries Exhibition, London, 1883, were 

 obtained from Singapore. They weighed 3cwt. 3qrs. i4lbs., and measured three feet four 

 inches in length. This record could, undoubtedly, have been easilj' beaten from the Queens- 

 land Barrier, had the necessary time and money been expended in searching for, and trans- 

 porting, the bulkiest specimens. Rumours are indeed rife along the Barrier district, and more 

 especially within striking distance of Cooktown, of huge monsters over ten feet long, and 

 weighing at least a ton. Such specimens inhabit deeper water, and the labour and appliances 

 necessary to raise them from their rocky bed are not forthcoming without special inducements. 

 The prodigious dimensions of as much even as fourteen feet were reported on one occasion to 

 Captain G. P. Heath, R.N., Portmaster of Queensland, from the reefs off Cooktown. The freely- 

 offered use of such boats and gear as might be required for transporting this monster of the deep 

 from its coral fastness did not, it is to be regretted, result in its successful capture. The great 

 Barrier Sea-serpent, run to earth in a succeeding chapter, was at this critical time, it may be 

 mentioned, awaiting discovery. 



A fallacy very widely prevails concerning the growth-conditions of the Giant Clam. It 

 is commonly stated, in popular works on natural history, that the animal is firmly attached to the 



