HOUTMAN'S ABROLHOS. 141 



manifold conditions, forming independent islets, clothing exclusively the precipitous 

 sides of the submarine cliffs with tier upon tier of its horizontal fan-shaped coralla, 

 or constituting but one among the many varieties entering into the composition of 

 the larger reefs. It is as seen growing on the perpendicular walls of the deeper 

 reef edges that it furnishes the most remarkable spectacle, often occurring under these 

 conditions in such luxuriance as to be visible in superimposed tiers or terraces as far 

 down through the clear water as the eye can penetrate. A specially favourable 

 opportunity of studying this coral growth was afforded the author on one of his 

 return voyages from the Abrolhos Islands, when owing to lack of wind the 

 lugger drifted and grounded for some little time, fortunately at low water, on the 

 margin of one of these hanging coral gardens. Shortly after the vessel drifted loose 

 again with the rising tide, a unique sight presented itself by the appearance of a 

 company of sharks, no less than fourteen, ranging from eight to ten or twelve feet 

 in length, being discernible at one time from the boat's deck. Without wishing to 

 cultivate their nearer acquaintanceship, one could not withhold admiration of the 

 leisurely grace of their motion as seen at various depths in the emerald clear 

 water, and of the amazing swiftness, like the release of an arrow from a bow, with 

 which they would abruptly dart away in pursuit of some passing fish, or in a race 

 for an attractive lure thrown to them from the boat. 



To return to the subject of the Abrolhos corals, there was one form developed 

 under conditions closely corresponding with the last-mentioned type, but notable for its 

 usually pale sage-green hue, and the remarkable diversity in the contour of its coralla. 

 In some instances, it formed robust, shortly branching, bush-like growths ; in others, 

 fan-like expansions, or even encrusting masses, or it might be a combination of these 

 types. Two characteristic illustrations of this coral, which is apparently an undescribed 

 species, but allied to Madrepora sarmentosa, also a new species collected by the writer 

 on the Great Barrier Reef, are given in Plate XXV. In the upper of these two, the 

 encrusting character of the initial or basal growth-stage of the species is very obvious. 

 A third and remarkably fine example of this coral, obtained in the south entrance 

 to Shark's Bay, which measures over three feet across, figures as a tailpiece 

 to this Chapter. It combines in its individual corallum so many noteworthy 

 variations that detached fragments from separated areas might be readily mistaken 

 for distinct species. All of these specimens figured, together with several additional 

 ones, have been contributed by the author to the British Museum Coral Galleries. 

 They there constitute a most instructive object lesson for the benefit of those syste- 



