GEOGRAPHICAL DISTRIBUTION OF CRUSTACEA. 147J 



Pacific Regions. A comparison of the regions of the Atlantic and 

 Pacific, and especially of the limits of those commencing at the South 

 American coasts, brings out some singular facts. 



The Torrid region of the Pacific, near the American coast, embraces 

 only seventeen and a half or eighteen degrees of latitude, all but three 

 of which are north of the equator ; while that of the Atlantic covers a 

 long range of coast, and reaches to 15 south. The south Subtorrid 

 Region has a breadth of about three degrees on the Peruvian coast, 

 reaching to 4 south, while that of the Atlantic extends to Rio 

 Janeiro, in 24 south. The Warm Temperate Region has a breadth of 

 less than a degree, reaching to Cape Blanco, in 4J south, while that 

 of the Atlantic extends to Rio Grande, in 33 south. The next or 

 Temperate Region has a longer range on the South American coast, 

 extending to Copiapo, in 27 i south, and the Atlantic region corre- 

 sponding goes to Maldonado in 35 south. The Cold Temperate 

 Regions of the two oceans cover nearly the same latitudes. 



On the North American coast at Cape Hatteras, the three isocrymes 

 62, 56, and 50 F., leave the coast together; and in the Pacific on 

 the South American coast there is a similar node in the system of 

 isocrymes, the three 74, 68, and 62, proceeding nearly together 

 from the vicinity of Cape Blanco. 



Viewing these regions through the two oceans, instead of along the 

 coasts, other peculiarities no less remarkable are brought out. The 

 average breadth of the /South Torrid Region in the Pacific, is more 

 than twice as great as that of the same in the Atlantic; and the most 

 southern limit of the latter is five degrees short of the limit of the 

 former in mid-ocean. So also, the Subtorrid Region at its greatest 

 elongation southward in the Atlantic, hardly extends beyond the 

 average course of the line of 68 F. in the Pacific, and the average 

 breadth of the former is but two-thirds that of the latter. The same 

 is true to an almost equal extent of the Warm Temperate and Tem- 

 perate Regions. 



The breadth of the Torrid Region of the Pacific to the eastward, 

 where narrowest, is about six degrees ; and to the westward, between 

 its extreme limits, forty-nine degrees. The Torrid zone or Coral-reef 

 Seas, in the same ocean, has a breadth near America, of about eigh- 

 teen degrees, and near Australia and Asia, of sixty-six degrees. 



New Zealand lies within the Subtemperate and Cold Temperate 

 Regions, excepting its southern portion, which appears to pertain like 



