CONTINENTAL SHELF 



239 



FIG. 169. GORGONIA, A SEA-FAN. 



FIG. 168. PENNATULA, A SEA- 

 PEN ("BLAKE"). 



FIG. 170. GORGONIA, SHOWING 

 THE POLYPS IN CONTRACTION 

 AND EXPANSION. (Fics. 169 

 AND 170 FROM LANKESTER'S 

 "TREATISE ON ZOOLOGY," BY 

 PERMISSION OF MESSRS. BLACK.) 



