ramparts which may be divided into an outer and an 

 inner series (see figure 3) . The latter encroaches more 

 or less into the lagoon channel. Each reef has for its 

 outer edge an enormous mass of coral growing just 

 below the surface and forming huge boulders and pin- 

 nacles (Figure 4) . These reach out under the breakers 

 and form to seaward a steep rough cliff which merges 

 below the zone of active growth into a slope of dead 

 coral rock, knov/n as the talus slope. Behind the outer 

 edge, the crevices and gullies between the coral be- 

 come filled with coral fragments broken off by storm 

 waves and thrown into quieter water. Still further to 

 the lee of the reef the interstices of rock become filled 

 with sand, small growing corals and coralline algae and 

 the rock becomes cemented into a crude pavement or 

 platform. This pavement is bordered to the leeward by 



Figure 4. Section of the outer edge of a reef. Nof to scale. 



2 3 



