A WARM-TEMPERATE MARINE FAUNA 



25 



Lower California, 



ocean coast, 30° N 

 Lower California, 



ocean coast, 28° N 

 Lower California, 



Cape San Lucas, 



23° N 



Feb. Aug. 

 16° C 15° C 



17-18 19 



21 



27 



English Channel, SW 

 mouth, 48-50° N 



Cape Blanco, W 

 Africa, 21° N 



Cape Verde, W 

 Africa, 15° N 



Feb. Aug. 

 9°C 17° C 

 18-19 20 



19-20 



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The following figures are given by Ekman (1953, p. 209, after 

 Schott, 1935) for surface temperatures along Pacific South America: 



Chiloe,43° S 

 Iquique, 20° 20' S 

 Callao (Lima), 12° S 



Feb. Aug. 



16° C 9.5° C 



19 15.5 



19 16 



It will be observed that Chiloe, with temperatures of 16 and 9.5° C, 

 compares with the English Channel, with temperatures of 9 and 17° C, 

 taking into account the reversal of seasons. But, as the dividing point 

 between the cold-temperate and warm-temperate regions, Chiloe Island 

 corresponds faunistically, not to Pta. Eugenia at Latitude 28° N, but 

 to Pt. Conception at Latitude 34° 30' N, which has an August mean 

 temperature of 16.5° C according to Ekman (1953, fig. 45, after 

 McEwen, 1912). (A comparable August figure for Pt. Conception of 

 16° C and a February figure of 13.5° C, based on averages of bucket 

 temperatures to 1946, were obtained from the Scripps Institution of 

 Oceanography.) Thus the mouth of the English Channel corresponds 

 more closely to Pt. Conception than to Pta. Eugenia, if both winter 

 and summer, and not just summer temperatures be taken into account. 



Finally, the reasons why neither Chiloe Island nor Pt. Conception 

 is a total barrier to cold-water species might be considered. The pre- 

 vailing currents, the Peru in the south, the California in the north, are 

 cold water currents. Directed from the poles toward the Equator, they 

 tend to constrict the warm tropical water to a band of narrow width, 

 from 23° N to 6° S Latitude. It is evident that they must similarly 

 compress and force equator-ward the warm-temperate waters on either 

 side of the tropical-water belt. Furthermore, they are constantly replenish- 

 ing warm-temperate waters with larval forms of cold-water decapod 

 crustaceans. That these boreal and Anti-boreal littoral species, the long- 

 range species, are able to persist in a warm-temperate situation is due 

 not so much to their eurythermy as to the upwelling of cooler sub-surface 

 water that occurs most pronouncedly at certain localities in these mid- 

 latitudes. It has been increasingly apparent of late that the range of 

 the cold-water littoral forms in the lower latitudes is not continuous, 



