Plate 4. 



Figs. 1, la. Organ-pipe coral, Tubipora sp. Fig. 1, upper surface ; fig. la, side 

 view, both natural size. 

 2,2a. Blue coral, Heliopora coerulea (Pallas). Fig. 2, corallum, natural 

 size; fig. 2a, surface, X 6. 



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