GEOGRAPHICAL DISTRIBUTION OF CRUSTACEA. 1469 



to the east. Its least width is four degrees of latitude ; 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 (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. 



2. Atlantic Subtorrid Regions, betiveen 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 temperature limits, a part of 

 the east coast of Florida, between 24° and 27 i ° 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 2 °, 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 under the tem- 

 perature of any part of the Torrid zone, the geographical 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 many 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, 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. 



The southern of these regions averages five degrees in width. The 

 eastern limit on the African coast is sixteen to eighteen degrees to the 

 north of the western on the South American coast. 



Atlantic Temperate Regions, between 62° and 56° F. — .The north 

 Temperate Region is but a narrow strip of water on the west, termi- 

 nating at Cape Hatteras, on the coast of the United States. To the 



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