32 
ZOOLOGY. 
The common red coral (Corallmm rithrum) of the Med- 
iterninean Sea is worked into various ornaments. The 
coral fishery is pursued on 
the coasts of Algiers and Tu- 
nis, where assemble in the 
winter aud spring from two 
hundred to three hundred 
vessels. The coral fishermen, 
with large rude nets, break 
off the coral from the sub- 
merged rocks. About half 
a million dollars' worth of 
coral is annually gathered. 
Of the larger corals the 
Madreporaria in the main 
are the true reef-builders. 
They are confined to waters 
in which through the coldest 
winter months the tempera- 
ture of the water does not 
fall below G8° F., though 
usually the waters are much 
warmer than this, the mean 
annual temperature being 
about 73i° P. in the North 
Pacific and 70° P. in the 
South. Coral reefs are abun- 
dant in the West Indies, but 
still more so in the Central 
Pacific, where there are a 
much greater number of spe- 
cies of corals. Along the 
Brazilian coast, as far south 
as Cape Frio, are coral reefs. 
In depth living coral-reef- 
builders do not extend more than fifteen or twenty fathoms 
below the surface. 
