216 THE POPULAR SCIENCE MONTHLY 



■■ 



The Lithothamnion Ridge along the Seaward Face of the Southeast Reef of 



Maee Island, Murray Islands. 



bryozoa which are remarkable lime-secreting organisms related more 

 closely to the worms than to any other phylum of the animal kingdom. 



This lithothamnion ridge thrives only where the breakers strike in 

 full force upon its living barrier, and it serves as the chief protector of 

 the island, breaking the force of every wave that approaches the wind- 

 ward shore. 



Clustered in the tide pools of this lithothamnion ridge, with the 

 waves dashing constantly over them one finds living corals which cling 

 tenaciously to the shallow crevices and grow into thin encrusting forms 

 instead of into dome-like shapes as in more protected waters; or their 

 branches are remarkably short stump-like and gnarled and tend to bend 

 inward toward the shore after the manner of the ragged trees that 

 survive along a wind-swept coast. 



At Maer Island, the lithothamnion ridge extends along the extreme 

 outer edge of the southeastern reef between 1,800 and 2,200 feet from 

 shore, and it forms a veritable dam which prevents the escape of the 

 water from the basin of the reef-flat at the lowest tides, so that at the 

 low tide of the springs, one finds here a great shallow marine lake about 

 1,700 feet wide, 2| miles long, and only about 18 inches deep. 



About 3,600,000 coral heads grow upon the hard rocky bottom of 

 this natural aquarium, and in the middle region of the reef-flat, 1,000 

 feet from shore, fully 50 per cent, of the bottom is covered with heads 

 the dominant species being the delicate and profusely branched Seria- 

 iopora histrix which forms a veritable coral forest, growing so luxuriantly 

 that no other species can thrive so well in this region as it does nearer 

 shore or farther out upon the reef. It is evident that there is a struggle 

 for existence between the different sorts of corals, and the Seriatopora 



