26 THE GREAT BARRIER REEF. 



embraces, their promiscuous plan of intermixture, but, at the same time, separation into distinct 

 groups by intervening water-spaces, combine to form what may be denominated a well-balanced 

 picture. The coral patch on the right-hand side of this reef-scape is noteworthy for its luxuriant 

 growths of Stags'-horn Madrepores, which embrace, in the immediate foreground, three or four 

 separate species, distinguishable in their living condition, not only with reference to their relative 

 dimensions and contours, but also by their diverse colouring. The most robust species, having 

 onl}' a few simple bifurcations elevated above the surface of the water, represents that more 

 massive form of Madrepora dccipicns which is delineated on Plate IX., Fig. 5, of the chromo- 

 lithographs, whose living tints, as there indicated, are not unusually pale primrose-yellow 

 throughout, with the exception of the terminal-growing inch, which is a delicate rose-pink. To 

 the rear of this larger species is a denser clump of the finely-branching form Madrepora pidcJira, 

 having the larggr terminal calicle of each branchlet turquoise-blue, while the remainder of the 

 corallum is straw-colour or light buff. A little to the rear of these occur the branching coralla of 

 Madrepora hebes and M. sccitnda, the former, in this instance, being a rich brown with white 

 growing tips, while the latter, as in the small fragment reproduced in Chromo plate IX., Fig. 7, is 

 coloured throughout an intense violet. Luxuriant growths of Madrepora millepora, noticed in 

 association with the preceding plate, two or three massive Astrasaceae, and a remarkably fine 

 hemispherical colony-stock of Pocillopora dainicoriiis, represent the remaining most prominent 

 coral varieties on the right-hand side. 



The more extensive, irregularly broken-up coral patch towards the left contains but few 

 visible specific varieties that are not represented in the right-hand section. The outljang strip in 

 the farthest distance is noteworthy as being composed almost exclusively of an unmixed growth 

 of Madrepora hebes. The most interesting feature on this side, however, is the large Frilled 

 Clam, Tridacna compressa, snugly ensconced on the lee side of the Goniastrasa in the imme- 

 diate foreground. This very fine example of the species measures about one foot in length. A 

 younger and much smaller specimen of the same bivalve may be observed, though not very 

 distinctly defined, embedded in a crevice towards the left in the upper surface of the same coral 

 mass. The gorgeous colours of the exposed mantle-surfaces of these mollusca have already been 

 a subject of comment in association with Plates IV. and VI. 



PLATE XVI. 



CRESCENT REEF, OUTER BARRIER SERIES, NO. 6. 



Low Woody Island again supplies the material for this reef-scape. It illustrates, undoubtedly, 

 the most luxuriant expanse of living coral (condensed into a relatively narrow area) that the author 

 has had the good fortune to photograph. The genus Madrepora, as is distinctly evident, enters 

 most extensively into the composition of this reef. Conspicuously to the front, on the left-hand 



