illustrating the Distribution of Marine Animals. 207 



in the ocean which gave Vaillant 76° F. 5 in August, afforded 

 Fitzroy (4° north, 96° west), on March 26 (when the sun had 

 long been far north), 82^° F. This fact shews the variations 

 of temperature that take place with the change of season. 



Remarks on the several Temperature Regions. 

 The form and varying breadth of the different regions, 

 and the relations between the sea-temperatures of coasts in 

 different latitudes which they exhibit, are points demanding 

 special remark. The conclusions are of much interest, al- 

 though some changes in the chart will undoubtedly be re- 

 quired by future researches. 



Atlantic Torrid Region, between 74° F. north, and 74° F. 

 south. — The form of this region is triangular, with the vertex 

 of the triangle to the east. Its least width is four degrees 

 of latitude ; its greatest width between the extreme lati- 

 tudes is forty-six and a half degrees. On the African coast 

 it includes only a part of the coast of Guinea, and no portion 

 is south of the equator. On the west it embraces all the 

 West India Islands and reefs (excepting the Little Bahama), 

 and the South American coast, from Yucatan to Bahia, — a 

 fact that accounts for the wide distribution of marine species 

 on the American side of the ocean. 



Atlantic Subtorrid Regions, between 74° and 68° F. — The 

 North Subtorrid Region of the Atlantic is about six degrees 

 in its average width, which is equivalent to a degree of Fahr- 

 enheit to each degree in surface. It incloses within the 

 same temperature limits a part of the east coast of Florida, 

 between 24° and 27£° north, and a part of the African coast, 

 between the parallels of 9° and 14|° north, the two related 

 coasts differing ten degrees in latitude. The Bermudas, in 

 latitude 33°, and the Cape Verdes, in 15^°, fall within this 

 region. 



The South Subtorrid Region has the same average width 

 as the northern, 



Taking the whole Atlantic Torrid or Coral-reef zone to- 

 gether, its width on the east is about twenty-one degrees, 

 while on the west it extends between the parallels of 30° 

 south and 34° north, a breadth of sixty-four degrees. As 



P 2 



