CCELENTERATA, 
255 
Fig. 20&.—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 cup-like depres¬ 
sion at. the top of a coral skeleton 
is called calicle. 
Fig. 207.—Fragment of Red Coral ( Coral- 
Hum, rubrum), showing living cortex 
and expanded Polyps. Mediterranean. 
