illustrating the Distribution of Marine Animals. 195 



isocryme of 68° F. ; the second, the Temperate zone of the 

 oceans, or the surface between the isocrymes of 68° F. and 

 35°F,; the third,ike Frigid zone,or the waters beyond the iso- 

 cryme of 35° F. 



I. TORRID OR CORAL-REEF ZONE. 

 Regions. Isocrymal limits. 



1. Supertorrid, . . . 80° F. to 80° F. 



2. Torrid, . . . .80° 



3. Subtorrid, . . .74° 



to 74° 

 to 68° 



II. TEMPERATE ZONE. 



1. Warm temperate, 



2. Temperate, 



3. Subtemperate, 



4. Cold temperate, 



5. Subfrigid, 



1. Frigid, 



A ninth region- 



III. FRIGID ZONE 



68° 

 62° 

 56 c 

 50 c 

 44 c 



to 62° 

 to 56° 

 to 50° 

 to 44° 

 to 35° 



35° to 26° 



■called the Polar — may be added, if it 

 should be found that the distribution of species living in the 

 frigid zone requires it. There are organisms that occur in the 

 ice and snow itself of the polar regions ; but these should be 

 classed with the animals of the continents ; and the conti- 

 nental isotherms or isocrymes, rather than the oceanic, are 

 required for elucidating their distribution. 



It seems necessary to state here the authorities for some 

 of the more important positions in these lines, and we there- 

 fore run over the observations, mentioning a few of most 

 interest. There is less necessity for many particulars with 

 reference to the North Atlantic, as our facts are mainly de- 

 rived from Lieut. Maury's chart, to which the author would 

 refer his readers. 



1. North Atlantic. — Isocryme of 74° F. — This isocryme 

 passes near the reefs of Key West, and terminates at the 

 north-east cape of Yucatan ; it rises into a narrow flexure 

 parallel with Florida along the Gulf Stream, and then con- 

 tinues on between the Little and Great Bahamas. To the 

 eastward, near the African coast, it has a flexure northward, 

 arising from the hot waters along the coast of Guinea, which 

 reach in a slight current upward towards the Cape Verde 



