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- 
Fig. 206.—Cell of Madrepore Coral, 
magnified. The chp-like depres¬ 
sion at the top of a coral skeleton 
is called calicle. 
Fig. 20T.— Fragment of Red Coral (Coral- 
Hum rubrum ), showing living cortex 
and expanded Polyps. Mediterranean. 
