208 J. D. Dana on an Isothermal Oceanic Chart, 



many species will thrive under the temperature 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 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 Hat- 

 teras, off the Carolinas, Georgia, and Northern Florida. 

 These shores and the Canaries are therefore in one and the 

 same temperate 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, terminating at Cape Hatteras, and having no place 

 on the coast of the United States. To the east it widens, 

 and embraces the Azores, and the African coast along Mo- 

 rocco, together with the Straits of Gibraltar, and a large 

 part of the Mediterranean. Madeira lies upon its southern 

 limit. It is, therefore, natural that the same species should 

 occur at the Azores, Madeira, and on the African coast, and 

 be excluded wholly from the Atlantic coast of Europe. This, 

 according to Prof. Forbes, is the fact with the Littorina 

 striata, besides other species. The coasts of Portugal and 

 the Azores are in different regions. 



The South Temperate Region extends to Maldonado at 

 the mouth of the La Plata, from near the parallel of 30° ; 

 along the African coast it reaches over more than twice the 

 number of degrees of latitude, to within five degrees of Cape 

 Town. 



Atlantic Hubtemperate Regions, between 56° and 50° F. — 

 The northern of these regions, like the preceding, can not be 

 distinguished on the coast of the United States, as the lines 

 of 50° and 56 ' F. with 62° fall together at Cape Hatteras. 

 On the eastern side of the Atlantic it occupies the coast of 



