illustrating the Distribution of Marine Animals. 211 



Indian Ocean Regions. — The Torrid Region covers the 

 larger part of the Indian Ocean, including all north of the 

 equator, and embracing the larger part of Madagascar. The 

 Subtorrid extends just beyond Port Natal on the African 

 coast (four degrees of latitude north of Cape Town), where 

 there are coral reefs, and also covers the northern part of 

 the Red Sea. The Warm Temperate and Temperate regions 

 each claim a part of the South African coast, and the latter 

 terminates at Cape Lagulhas. 



It hence follows that Port Natal, in latitude 30° south, the 

 Hawaiian Islands, and Bermudas, lie within regions of 

 the same name ; while Cape Town, in latitude 34° south, is 

 in a like region with northern New Zealand, Valparaiso, 

 the Atlantic shores of Portugal, and the sea between Cape 

 Hatteras and Cape Cod. 



The areas of the Torrid, Temperate, and Frigid zones of 

 ocean temperature, either side of the equator, considering 

 27° as the normal limit between the first two of these zones, 

 and 56° the limit between the Frigid and Temperate, are as 

 follow : — 



Torrid zone, 33,711,200 square miles (geographical) 



Temperate zone, 27,849,500 „ ,, 



Frigid zone, 12,694,700 „ „ 



It is hence seen that the Temperate zone, although two 

 degrees wider than the Torrid, has not as large a surface. 

 The species of marine life, if distributed equally over the 

 two, would, therefore, be one-fifth more numerous in the 

 Torrid zone than in the Temperate, unless the extent of 

 ocean and coast-line were far greater in the Temperate than 

 in the Torrid zone, which is not the case. The ocean in the 

 southern Temperate is much more extensive than that of the 

 southern Torrid ; but the coast-line is far less extensive in 

 the former, as it does not abound in islands like the Torrid 

 zone.* It is difficult to fix upon exact ratios, and we do not 

 attempt it. 



The range of temperature is far greater in the Temperate 



* The following table gives very closely the surface of the zones in square 

 geographical miles, for every 2£ degrees of latitude to the parallel of 60° : it 

 is deduced from a larger table by Berghaus, in his Lander unci Volker-kundp, 



