CONTINENTAL SHELF 



239 



Fig. 168. — Pennatula, a Sea- 

 Pen ("Blake"). 



Fig. 170. — Gorgonia, showing 

 the Polyps in Contraction 

 and Expansion. (Figs. 169 

 and i70 from lankester's 

 "Treatise on Zoology," by 

 permission of Messrs. Black.) 



