Sentence:  As the Nautilus headed for Clermont-Tonnere, one of the curious islands of the group discovered in 1822 by Captain Bell of the Minerva, I prepared to study the <WSD>madreporal</WSD> system that has created these particular isle. 
Meaning of the word marked with <WSD> tags:  Characteristic of or associated with reef coral of genus "Madrepora"; madreporic.