224 



THE OCEAN WORLD. 



ISIDIN^. 



The Isidince constitute an intermediate group between the Gor- 

 qonitia: and Corallina. Their polypidom is arborescent, but its axis is 



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ir.,,. ;lr , 



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m. 







Fig. 82. — Isis hippuris. 



formed of articulations alternately calcareous and horny. The prin- 

 cipal genus is that called Isis, which is met with in the Indian Ocean, 

 on some parts of the Amtrican coast, and in the Pacific Ocean, 



