32 



ZOOLOGY. 



The common red coral {C'orallium rubrum) of the Med- 

 iterranean Sea is worked into various ornaments. The 



coral fishery is pursued on 

 the coasts of Algiers and Tu- 

 nis, wl)ere assemble in the 

 winter and spring from two 

 hundred to three hundred 

 vessels. Tlie coral fishermen, 

 with large rude nets, lireak 

 oil tlie coral from the sub- 

 merged rocks. About half 

 a million dollars' worth of 

 coral is annually gathered. 



Of the larger corals the 

 Madrqjoraria in the main 

 are the true rcef-builders. 

 They are confined to waters 

 in which through the coldest 

 winter months the tempera- 

 ture of tlie water does not 

 fall below C8° F., tliough 

 usually the waters are much 

 warmer than this, the mean 

 annual tcmjierature being 

 about 73^° F. in the North 

 Pacific and 70° F. in tlie 

 Soutli. Coral i-cefs are al)un- 

 dant in the West Indies, but 

 still more so in tlie Central 

 Pacific, wliere tliere are a 

 mucli gi'cater 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 falhoms 

 below the surface. 



