224 



THE OCEAN WORLD, 

 ISIDIN/E. 



The Isidina constitute an intermediate group between the Gor- 

 gonince and Corallines. Their polypidom is arborescent, but ks axis is 



Fig. 82. Isis hippuris. 



formed of articulations alternately calcareous and horny. The prin- 

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

 on some parts of the American coast, and in the Pacific Ocean. 



