96 CORALS 



distinctly capitate in Australian Barrier Reef specimens 

 (Saville-Kent). 



The arrangement of the mesenteries in Porites is very 

 similar to that previously described in Madrepora, and the 

 increase in the number of mesenteries also takes place by 

 the addition of bilateral pairs in the space between the 

 mesenteries of one pair of directives. 



The colour of the Porites is very variable and often 

 very brilhant. Duerden ^ writes that "Porites astraeoides 

 (of Jamaica) is one of the most gaily coloured of all the 

 West Indian corals, and occurring in large masses often 

 becomes an important constituent in determining the general 

 coloration of the reefs. As a rule the colonies are a bright 

 blue, pale yellow, or yellowish-green. Various colours occur 

 side by side, and sometimes one portion of a colony will be 

 blue and another yellowish-green." 



Saville-Kent says of the colours of Porites on the Great 

 Barrier Reef, " A light ochre, dark and golden or mustard 

 yellow, and brown are the prevailing colours among the 

 arborescent types. The surface of the corallum in the 

 massive species, however, is often a delicate pink, a light or 

 bright lilac, or (more rarely) pale yellow." 



The genus Goniopora is closely related to Porites and 

 also builds up great masses of spherical, lobate, encrusting 

 coral. It appears to be more restricted in its recent geo- 

 graphical distribution than Porites, being confined to the 

 tropical Indo-Pacific regions. The principal characters by 

 which it can be distinguished from Porites is the presence 

 of a secondary series of twelve septa, so that there are 

 twenty-four septa in each calyx instead of only twelve. 



The polyps are said to be very extensile and to possess 

 usually twentv-four long digitate tentacles arranged in a 

 single ring. 



We have at present no knowledge of the number and 

 arrangement of the mesenteries or other details of anatomical 

 structure. 



MoNTiPORA. — The genus Montipora is another important 

 reef-building coral, widely distributed in the tropical seas of 



^ J. F. Duerden, Mem. Nat. Acad. Sci. Washington, vol. viii., 1902, p. 550. 



