situation. Moreover, even in a single species, the form 

 and appearance of the coral may vary very greatly de- 

 pending upon the nature of the surroundings. In rough 

 water there is a tendency towards more massive or 

 encrusting growth or to the development of short thick 

 branches in branching forms. Where the water is quieter 

 conditions are more conducive to diffuse branching or 

 to thin projecting plates. In deeper water, below the 

 region of greatest wave action, the spindle shaped or 

 pillar like form is encouraged. 



As an example, the finger coral, Porites porites, is 

 more openly branched with more slender branches in 

 shallow relatively quiet water. On the reef itself, where 

 wave action is more vigorous, the same species is more 

 compactly branched and each finger is short, thick and 

 stubby. The brain coral, 'Diploria clivosa, forms a low 

 encrusting growth in regions of heavy surge, but in 

 deeper water, where it is less exposed to wave movement, 

 it tends to become more massive and to develop knobs 

 and blunt projections. 



Species found in the region of heaviest wave action 

 on the exposed reef are usually the massive or boulder 

 type, such as TAontastrea annularis, the brain corals, the 

 porous coral, Voriles astreoides and the starlet coral 

 Siderastrea siderea. There are also thick branching forms 

 like the elkhorn coral, Acropora palmata and, in the 

 outermost part of the reef, the thick columns of 'Den- 

 drogyra cylindrus, the pillar coral. There are no fragile 

 branches or unattached species. 



At the opposite extreme of living conditions, in 

 shallow water where sediment is present, are to be seen 

 the finger coral, Vorites furcata, and also the more 

 slender form of Vorites porites, the clubbed finger coral. 



56 



