PHOTOTYPE PLATES NOS. XIX. AND XX. 31 



regions of the tropics, being especially abundant in the vicinity of Thursday Island, but 

 apparently absent on the reefs visited south of Torres Strait. The scene of this particular 

 view, which embraces so rich a collection of Alcyonaria, is the Madge Reef, laid bare at 

 spring-tides only, in the channel that separates Thursday and Prince of Wales Islands. 



PLATE XX. 



(S.)-]lLCYONaRmN REEF, THURSDM ISMND, NO. 2. 



The site of this reef-scape is adjacent to that of the preceding one, being situated on an 

 extremity of Madge Reef, with portions of Thursday and Prince of Wales Islands visible on 

 the right and the left hands respectively. As in Plate XIX., the Alcyonaria monopolise the 

 largest share of the exposed reef A few stony corals, including, towards the central foreground, 

 two or three spreading coralla of Madrcpora prostrata, and a depressed, symmetrically ovate 

 one of a species of Cj-phastraea, are the most conspicuous members of their order. Among 

 these, the Madreporse, almost without exception, already indicate the presence of parasitically 

 attached Alcyonarian polyparies, and are, in consequence, threatened with early extinction. 



The species of Alcyonaria recognisable on this reef include the two types, Sarcophyton glait- 

 ciiiii and Alcyonium flexibile, associated with the preceding illustration. There is also an extensive 

 growth of a species, having a minutely nodulated polypary, that is apparently referable to the 

 genus Ammothea. The most remarkable representative of the Alc^'onarian order visible in this 

 reef-scape is undoubtedly, however, the symmetrical form, several feet in diameter, with uni- 

 lateraily-Iobate radial plications, that fills a large area of the foreground on the left-hand side. 

 In its general contour the pol3'pary of this species appears to coincide very nearly with that of 

 the Alcyonitiiii latum reported by Dana from Fiji, with the name of which it is provisionally 

 associated. In the Thursday Island example the polypar}' was coloured a rich golden- 

 brown, while that reported from Fiji was green. A corresponding, or even greater, difference 

 of tint may, as already recorded of SarcopIiyto7t glaiicitiii, obtain among individuals of the same 

 species. 



(B.)-SLCYONflRmN REEF, THURSDM ISLAND, NO. 3. 



This picture, also from the Madge Reef, Thursday Island, graphically illustrates the re- 

 markable development to which an individual Alcyonarian polypary may attain. From the fore- 

 ground to the water's edge in the middle distance, a width of at least fifty or sixty feet, the entire 

 superficial area is encrusted by one continuous rugose polypary of the Alcyonium murale of Dana. 

 In its course of growth this polypary has, as evidenced by the local irregularities, overgrown many 

 Madreporarian coralla, and it is as assuredly advancing against, and even beginning to encroach 



