MADREPORES. 



Ill 



PAVONIA LAdTUCA. 



Islands, is distinguished by the beautiful foliated 

 expansions of the calcareous axis, resembling a 

 cluster of cup-like flowers; each cup contains a 

 polyp. 



In the genus Astrcea, the polyps are situated in 

 deep polygonal laminated cells, and are connected 

 by a thin gelatinous expansion covering the dark 

 calcareous mass, which is generally of a convex or 

 rounded form, externally. When the polyps of the 

 Astrcea viridis protrude themselves, and expand their 

 numerous arms, consisting of a large and small one 

 alternately, they resemble beautiful green flowers 

 with a blue centre, the oral disc being tinted with 

 the latter colour. 



In other instances, we observe a collection of 

 tubes into bundles, like reeds bound together, and 

 open at one end, through which the polyps protrude, 



