DEPOSITION IN THE SEA 253 
ures cannot move about to seek their own food, they 
can thrive only where constantly moving currents 
bring an abundant supply; nor can they live where 
the water is muddy, as it is near the mouths of 
many rivers. The most favorable place for coral 
Fig. 143. 
Coral life on a part of the Great Barrier Reef, Australia. 
erowth is in the clear ocean water warmed and 
moved by the great currents. 
While the reef-building coral is so delicate that it is 
unable to live on most coasts, it is nevertheless found 
in profusion wherever conditions are at all favorable 
(Fig. 143). In the West Indies, on the coast of Florida, 
and among the Bahamas and the Bermudas, we have 
