iS THE GREAT BARRIER REEF. 



dnmicornis occupies the centre of the same reef-mass, while a large, isolated dome of a golden 

 brown Brain coral, Coeloria, monopolises the nearest foreground. 



NO. 2.-MILLEP0Rfl AND flLCYONflRIS, PORT DENISON. 



This illustration represents, practically, a more comprehensive view of the reef delineated 

 in Plate VII. The same coralla of Millepora, Symphyllia, and Coeloria, will be recognised in 

 the centre of the picture, while new growths are included in both the background and the 

 foreground of this central area. The isolated knoll, immediately to the front, supports a varied 

 assemblage of coral species. Most conspicuous among these are the leather-like polyparies of 

 Sarcopliyfoii g/aiiciiin, which vary in colour from pale apple-green or bronze-green to lilac or 

 golden-brown. These colours, as recorded in a later chapter, may change from time to time in 

 the same individual polypary. Throughout all variations in hue of the leathery matri.x, the 

 essential living factors, or slender-stalked, eight-armed polyps, are, without e.xception, yellow, 

 though e.Nhibiting gradations of this hue that may range from palest primrose to the brightest 

 cadmium. Illustrations of the diversely tinted polyparies of this Alycyonarian, together with 

 its characteristic polyps, are included in the Chromo plate series, No. X. A few of the yellow 

 polyps, in their semi-retracted state, may be distinctly discerned, with the aid of a hand-glass, 

 near the lower edge of the polypary, situated farthest towards the left, in the uppermost group 

 on this coral knoll. Closely associated, towards the back of this foreground mound, are coral 

 growths which represent in the order of their disposition the genera Symphyllia, Pocillopora, 

 and Millepora. The hemispherical mass that constitutes the main substance of this foreground 

 mound would appear to be the long since dead, and much eroded, corallum of a giant Brain- 

 stone coral, pertaining to the genus Coeloria. 



The rocks in the background of this reef-view are of interest, though, unfortunately, some- 

 what out of focus. The attached objects which impart to those rocks a rough, nodulated 

 appearance, are masses of the oyster, Osfrea mordax, of general occurrence throughout the 

 Barrier district, and fully described and illustrated under the appropriate chapter heading. 

 The interest attachable to these bivalves, in the present connection, is associated with the fact 

 that their presence serves to illustrate the respective horizontal planes where the molluscs first 

 appear, flourish, and cease to grow, the corals taking up the running. The most luxuriant 

 growth-zone of this oyster species, it may be remarked, is represented by, as nearly as possible, 

 half ebb of ordinary spring-tide. No corals are found growing at the vertical altitude of this 

 mid-tide oyster plane ; neither do the oysters descend to the coral zone. It will be obvious, 

 from these remarks, that epochs of exceptionally low spring-tides are the only seasons in 

 which these coral organisms can be approached for the purposes of study and photographic 

 illustration under their natural conditions of vitality. 



