CORALS AND CORAL-ANIMALS. 171 



Australian Barrier. The second species of Echinopora exhibiting a similar foliaceous, but more 

 robust and procumbent, growth-plan, and also collected on the Palm Islands reefs, would appear to 

 be identical with Echinopora aspcra. This species forms extensive prostrate or encrusting folia, 

 the surface of which, including both the polyp-cells and the intervening areas, is coarsely dentate 

 or serrated. The general ground colour of the corallum of this Echinopora is, as in the preceding 

 species, golden-brown, more or less variegated with green. The corallites or p olyp-cells are 

 considerably larger, being over half an inch in diameter; the oral area is coloured a bright brick- 

 red ; and, between this and the outer septal border there intervenes a conspicuous band of 

 brilliant green. This specific type has been collected by the author at Port Darwin, in the 

 northern territory of South Australia. 



A' trio of genera, coinciding with one another in the erect bush-like character of their coralla, 

 and more especially in the fact that their polyps are structurally identical, although not usually 

 included in the same family, may be conveniently treated together in these pages. The three 

 genera in question are those of Scriatopora, Stylopora, and Pocillopora. The first-named of 

 these is characterised by its bush-like aggregations, being composed ol slender cylindrical 

 stems that for the most part increase in height by continual bifurcation, and freely unite, or 

 anastomose, at every point of contact with the neighbouring branches. The polyp-cells or 

 corallites are very minute, circular, and arranged in symmetrical longitudinal series throughout 

 the extent of the branchlets. The polyps, which are so small that a pocket-lens is required 

 for their perfect observation, possess only twelve tentacles, which are short and very distinctly 

 knobbed. The coralla of the living colony-stocks of both this and the succeeding genus, 

 Stylopora, are among the most brilliantly coloured that occur throughout the coral class. The 

 prevailing tints are a bright rose-pink, or even magenta, the colours being most intense towards 

 the exposed distal extremities of the branchlets. The hidden, basal, portions are, on the other 

 hand, usually light fawn or buff, with which less striking colours the entire corallum may 

 occasionally be tinted. The minute, twelve-tentacled polyps are usually a lighter shade of the 

 same tint as the corallum, the inflated tips of the tentacles being somewhat the brightest. A 

 characteristic illustration of the conditions of growth of Seriatopora is furnished by Plate VI 11., 

 No. I, of the photo-mezzotype series, representing a Port Denison reef-scape. In this illustration 

 two colony-stocks of the pink variety of Scriatopora elegans or S. Iiystrix, one of them largely un- 

 covered by the tide, occupy a sub-central position somewhat towards the left hand. Representa- 

 tions of a small corallum, a branchlet, and the extended polyps of a living corallum of the same 

 species, are included in Chromo plate VII., Figs, i, ia, b, and c. A short, thick, acuminately- 

 branched representative of this genus, also obtained from the Barrier district, would appear to 

 be identical with Seriatopora octoptera. 



In the genus Stylopora, both the colouring of the living coralla and the structure of the 



contained polyps are precisely identical with those of Scriatopora. The essential distinctive 



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