GEOGRAPHICAL DISTRIBUTION OF CRUSTACEA. I479 



The Atlantic tropical current also flows in part down the eastern 

 coast of South America, giving a deep flexure to each of the isocrymes, 

 besides making these lines to diverge from the equator, through all 

 their length. Again, the polar current passes northward nearer the 

 coast-line, bending far back the western extremity of each of the 

 isocrymes. 



In the Pacific, the tropical currents show their effects near the coast 

 of New Holland and China, in a gradual divergence of the lines from 

 the equator. The ranges of islands forming the Tarawan, Radack, 

 and Ralick Groups, appear to divert the current northward in that 

 part of the North Pacific, and consequently the isocrymal lines bend 

 northward near longitudes 170° west and 180°; and near Niphon, 

 that of 68° shows a still greater northern flexure. 



The influence of the polar currents in this ocean is remarkably 

 great. The southern flows from the west and south, bending upward 

 the line of 56° F. along the South American coast, producing at Val- 

 paraiso at times a sea-temperature of 48° F. Still farther north, it 

 throws the line of 68° F. even beyond the equator and the Galla- 

 pagos ; and that of 74° F., nearly one thousand five hundred miles 

 from the coast, and -four hundred north of the equator. The line of 

 62° F. reaches even beyond Payta, five degrees south of the equator, 

 the sea-temperature at this place being sometimes below 61°. 



The north polar current produces the same result along the eastern 

 coast of Asia, as on the eastern of America. The isocryme of 74° F, 

 is bent southward from the parallel of 23° to 12° 30' north; and that 

 of 68° F. from 34° to 15° north, and the latter deflection is even longer 

 than the corresponding one in the Atlantic. The trend of the coast 

 opens it to the continued action of this current until the bend in the 

 outline of Cochin China, below which the cold waters have less 

 influence, although still showing some effect upon the heat-equator. 

 The isocryme of 44° is bent southward to Niphon, by the same cold 

 waters, and from this part of the northern Pacific the current appears 

 to flow mostly between the islands of Japan and the continent. 



In the Indian Ocean, the effects of the tropical current, as it flows 

 westward, are apparent in the southern deflection of the several iso- 

 crymes. The trend of the coast favours a continuation of the current 

 directly along the coast, and consequently, its modifying influence on 

 the sea-temperature reaches almost to Cape Town on the coast, and 

 passes even beyond it at sea, carrying 56° F. to the meridian of 15° 

 east. 



