1476 



CRUSTACEA. 



The areas of the Torrid, Temperate, and Frigid zones of tempera- 

 ture, either side of the equator, considering 27 as the normal limit 

 between the first two of these zones, and 60 the limit between the 

 Frigid and Temperate, are as follows : 



Torrid zone, 

 Temperate zone, 

 Frigid zone, 



8,427,000 square miles (geographical) 

 7,641,000 " " " 



2,486,300 " ", " 



It is hence seen that the Temperate zone, although six degrees 

 wider than the Torrid, has not as large a surface. The species of 

 marine life, if distributed equally over the two, would, therefore, be 

 more numerous in the Torrid zone than in the Temperate, unless the 

 extent of ocean and coast line were far greater in the Temperate than 

 in the Torrid zone, which is not the case. The ocean in the southern 

 Temperate is much more extensive than that of the southern Torrid ; 

 but the coast line is far less extensive in the former, as it does not 

 abound in islands, like the Torrid zone.* 



The range of temperature is far greater in the Temperate zone than 

 in the Torrid, it being 20 F. in the latter, and 33 F. in the former. 



In the Torrid zone, the Subtorrid Region has nearly one-third the 



* The following table gives very closely the surface of the zones in square geographi- 

 cal miles, for every 2J degrees of latitude to the parallel of 60 : it is taken from a 

 larger table by Berghaus, in his Lander- und Volker-kunde, i. 47. The first is the zone 

 from the equator to the parallel of 2}, the second, from 2} degrees to 5 degrees, and 

 so on. 



2} 



5 



7i 



10 



121 



15 



17i 



20 



22 i 



25 



27} 



30 



The zone from 60 to 70 has the area, 

 " 70 to 80 " " 



" 80 to 90 " " 



692,424 

 673,440 

 653,172 

 631,656 

 608,944 

 585,064 

 560,320 

 534,032 

 506,960 

 478,924 

 441,792 

 420,176 



1,366,748 

 837,516 

 282,036 



