1 84 THE GREAT BARRIER REEE. 



a warm pinkish-brown, the outer edge of the expanded vase, for a width of half an inch, pale Hlac, 

 while the terminations of many of the central sprigs were pink. The colours of the expanded 

 polyps, so far as observed, were found to correspond with those of the associated corallites. 



A group of the genus Madrepora which still awaits notice is the one that includes those 

 rarer, more massive, species, whose coralla take the form either of thick erect lobes or folia, or of 

 corrugated incrustations. A tj'pical representative of this subdivision is illustrated by Madrepora 

 cuneata, referred to on page 105, as constituting one of the most conspicuous species on the platform 

 reef that skirts Masthead Island in the Capricorn group. This platform is composed of a series 

 of shallow terraces, over which the water drains in a smooth pellucid sheet, at lowest ebb. 

 The surface of the reef, which would appear to be never completely bare of water, is almost 

 completely encrusted with the radiating ridges and irregular nodular coralla of the Madrepora. 

 The colour of the corallum in this species is usually light brown edged with white, and the 

 associated polyps are of clear brown. In a very closely allied deeper-water species, Madrepora 

 palifera, which builds up massive fronds or lobes, several feet in height, just outside the 

 platform's edge, both the prominent corallites and the associated polyps are a bright primrose- 

 yellow. With reference to the fact that there is no modified apical or terminal corallite in 

 these massive encrusting or foliaceous Madreporae, they have been referred by Dana to a 

 sub-genus bearing the distinctive name of Isopora. 



A genus of the Perforate corals that is so nearly allied to that of Madrepora that it is 

 held by some authorities to represent an imperfectly developed, or a degraded modification of 

 that generic group, is that of Montipora. The coralla in this genus commonly take the form 

 of thin encrusting, or free, widely-expanding, folia ; but they are in other instances represented 

 by more solid masses whose surfaces are, wholly or in part, developed into a variety of 

 lobate or tufted excrescences. The texture of the surface of the coralla of the members of 

 this genus Montipora is generally ornamented with what may be described as a sort of frost- 

 work of calcareous spicules, which is of extreme beauty as seen with the aid of the microscope. 

 The pattern is different in every species, and these spicular elements furnish valuable accessory 

 characters for the establishment of distinctions between what would otherwise appear, in many 

 instances, to be identical varieties. 



Several members of the genus Montipora enter conspicuously into the construction of the 

 Barrier reefs ; but, as they are most abundantly developed below the line of lowest spring 

 ebb, they are rarely uncovered. A fair illustration of the typical mode of growth of the 

 foliaceous varieties is afforded by the photographic reef-view reproduced in Plate IX., where, 

 in the foreground, towards the right hand, a somewhat broken-up colony-stock of Montipora 

 e.xpaiisa is conspicuous. Other coralla of the same species occupy a position immediately 

 beneath a luxuriant growth of Madrepora convcxa, a little to the rear. An allied species, Monti- 

 pora foliosa, or its near relative, is characteristically represented in the Warrior Island reef-view 



