CCELENTERATA. 



255 



Fig. 205. — Astrcea rotulosa. West Indies. 



The main kinds of reefs are fringing, where the reef is 

 close to the shore ; barrier, where there is a channel be- 



maguified. The cup-like depres- Fig. 20T. — Fragment of Red Coral (Coral- 



sioii at the top of a coral skeleton Hum rubrum), showing living cortex 



is called calicle. and expanded Polyps. Mediterranean. 



