lo THE GREAT BARRIER REEF. 



rate than the solid coralla of the Porites and Goniastrasa. It may consequently happen, within 

 the course of a few years, that this Madrepora shall have intruded so far into the dividing 

 channel as to exert a material influence on the inwardly approaching growths of the two more 

 massive genera. 



One other coral-growth of conspicuous dimensions, included in the diagram, invites 

 attention. This is a mass of the labyrinthine dark brown Symphyllia hemisphcrica, about three 

 feet in diameter, which is growing on the south-westerly outer rim of the Porites. Its 

 approximate size and position were duly charted; but the rapidly-rising tide inteivened to 

 prevent its precise measurement. 



In addition to the outermost reef-area, roughly outlined in Fig. i of the accompaying diagram, 

 careful measurements were taken, at the same date, of the longest diameters of the several 

 conspicuous coral-growths that form the immediate foreground of Plate II. The dimensions of 

 these more inshore coral-masses are indicated in Fig. 2 of the diagrammatic plan. They include, 

 towards the left, an irregularly-rounded, almost high and dry, mass of Goiiiastrcra Grayi, the 

 commonest dark-brown species of a genus which enters so extensivel}' into the composition of 

 all inshore or fringing reefs throughout the Barrier district. This genus will be found most 

 abundantly represented in the Palm Islands inshore reef, Plate IV., and also in the remarkable 

 Skull Reef, illustrated by Plate XIV. The extreme right of the foreground is occupied by the 

 dome-shaped corallum of one of the larger Brain-corals, Symphyllia, specifically identical with 

 the specimen growing on the outer rim of the large Porites. Both this and the Goniastraea last 

 referred to are, however, represented to much better advantage in the following plate. 



Among the coral-growths in the present reef-view, yet unnoticed, attention may be directed to 

 the smaller submerged Porites just awash in the central foreground, and having growing upon it 

 a Pocillopora that is almost completely dry. So soon as this Porites attains a few more inches of 

 vertical growth, its entire superior surface, it may be anticipated, will become dead and eroded, 

 after the manner of the large outlying mass that forms the main element of the diagrammatically 

 charted reef. 



The third figure in the accompanying diagrammatic plan includes a couple of coral-masses 

 that are located some twenty or thirty yards to the left, or east, of the foreground group in Plate 

 II. They were photographed and measured at the same date, but do not embrace distinctive 

 features requiring special illustration. It may be recorded, however, that the larger and nearer 

 mass is a dark-brown Coeloria with very short calicinal valle3's that appears to be identical with 

 Coeloria sinensis (M. Ed. and H.), which, as shown in the diagram, has its upper surface 

 obliquely weathered. The adjacent and hinder coral-stock represents a corallum of a Goniastraea 

 that is eroded exteriorly and centrally' in such manner as to exhibit a distinct crescentic outline. 



A conspicuous feature, not hitherto referred to, in the central portion of the exposed reef 

 in this photographic illustration, is the luxuriant development thereon of various species ol 



