GEOGRAPHICAL DISTRIBUTION. 351 
On the African coast there are coral reefs at Port Natal, 
in latitude 30° S. ; and here, owing to the warm currents from 
the tropical regions, the mean winter temperature of the water 
is not below 68° F. 
Passing from the Indian to the Atlantic Ocean, we find 
little or no coral on the west coast of Africa. The islands of 
Cape St. Ann and Sherboro, south of Sierra-Leone, are de- 
scribed as coral by Captain Owen, R. N., in the Journal of 
the Geographical Society (vol. ii, p. 89); but this has been 
since denied. The Island of Ascension, in 7° 56’S.,and 14° 
16’ W., must have been bordered by growing coral, as Quoy 
and Gaymard mention that a bed of coral rock may be seen 
buried beneath streams of lava. Quoy also states that the 
corals which formed these reefs are no longer found alive, and 
adds that volcanic eruptions have probably destroyed them. 
The cold polar currents along the western African coast are the 
cause of the absence of corals from it, to within six or seven de- 
grees of the equator; and these coid waters may at times ex- 
tend still farther north. The same obstacle to the diffusion of 
species eastward, mentioned as occurring in the Pacific—that is, 
westward currents—exists also in the Atlantic. 
On the American shores of the Atlantic, north of the 
equator, there are few reefs, except in the West Indies. The 
waters of the Orinoco and Amazon, and the alluvial shores 
they occasion, exclude corals from that part of the coast. 
In the West Indies, the reefs of Florida (p. 204), Cuba, 
the Bahamas (p. 213), and of many of the eastern islands are 
well known. On the east coast of Florida they continue up 
as far as Cape Florida, in latitude 25° 40’ N.; and reef-corals 
are living off Charleston, S. C., according to Prof. Verrill. 
There are also said to be patches at intervals along the coast 
