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, 



8,427,000 square miles (geographical) 



Temperate zone, 



7,641,000 « " " 



Frigid zone, 



. 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 2£ 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. 



21° 



. 809,824 



32 *° 



. 692,424 



5° 



808,200 



35° 



673,440 



7i° 



. 805,124 



37*° 



. 653,172 



10° . 



800,512 



40° 



631,656 



12*° 



. 794,368 



42J° 



. 608,944 



15° . 



786,728 



45° 



585,064 



m° 



. 777,580 



47*° 



. 560,320 



20° . 



766,952 



50° 



534,032 



22*° 



. 754,868 



52*° 



. 506,960 



25° . 



740,544 



55° 



478,924 



27*° 



. 726,408 



57i° 



. 441,792 



30° . 



710,092 



60° 



420,176 



The zone from 60° 



to 70° has the ar 



ea, . 



1,366,748 



a 7qo 



to 80° " < 



t 



. 837,516 



" 80° 



to 90° « i 



c 



282,036 



