314 On an Isothermal Oceanic Chart, illustrating 
Arr. XXXI.—On an Isothermal Oceanic Chart, illustrating the 
Geographical Distribution of Marine animals ; James D. 
Dana. 
(Continued from p. 167.) 
Remarks on the Several Temperature Regions. 
Tue form and varying breadth of the different regions, and the 
relations between the sea-temperatures of coasts in different lati- 
tudes, which they exhibit, are points demanding special remark. 
The conclusions are of much interest, although some changes in 
the chart will undoubtedly be required 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 lati- 
tude; its greatest width between the extreme latitudes, 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 (ex- 
cepting 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 Fahrenheit 
to each degree in surface. It encloses within the same tempera- 
ture limits, a part of the east coast of Florida, between 24° and 
274° north, and a part of the African coast, between the parallels 
of 9° and 143° north, the two related coasts differing ten degrees 
in latitude. The Bermudas, in latitude 33°, and the Cape Verdes, 
in 154°, 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 together, 
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 many species will thrive un- 
der the temperature of any part of the Torrid zone, the geograph- 
ical range of such species in the Atlantic may be very large, 
even from Florida and the Bermudas on the north, to Rio Janeiro 
on the south, a range of which there are actual examples. 
Atlantic Warm Temperate Regions, between 68° and 62° F. 
—The northern of these regions has a breadth of fourteen and a 
half degrees along the west of Africa, and about seven degrees 
along the United States, to the south of Cape Hatteras, off the 
Carolinas, Georgia, and northern Florida. These shores and the 
Canaries are therefore in one and the same temperature zone. 
