62 



in shore, owing to the cooling effect of the Arctic Current, there are 

 many forms that belong more strictly farther north ; while off shore, 

 maybe at no great distance, there are southern forms brought north- 

 ward beyond their limit by the warm waters of the Gulf Stream. In 

 this way are brought together, in closely adjoining regions, two dis- 

 tinct facies — forms which, without the influence of currents, would 

 have their proper habitat hundreds of miles apart. Sharp points of 

 land jutting out into the sea for several miles, in some cases many 

 miles, often mark the limit in range of certain forms, especially those 

 that love the simple life, preferring a quiet, shallow-water habitat; 

 for, in attempting to round such a point, the form would be carried 

 into depths it is unaccustomed to, or into bottom or shore condi- 

 tions different from those hitherto surrounding it, or else out to where 

 waves and currents are more vigorous than please its fancy. Cape 

 Cod, Cape Hatteras and Cape Fear are just such points along the 

 Atlantic coast that mark the limit of range for a goodly number of 

 species. Cape Hatteras, in addition, is the point where the Gulf 

 Stream is deflected off shore as it flows northward, and is also the 

 point where the Arctic Current, in its southward movement, ceases to 

 be a surface current and sinks beneath the Gulf Stream. For the rea- 

 son that Cape Hatteras marks the limit of so many forms in their 

 migration, it has been taken as the dividing point between northern 

 and southern forms. Those forms whose northern limit of geo- 

 graphical range is at Cape Hatteras, may be regarded as southern, 

 while those whose corresponding southern limit is at Cape Hatteras 

 may be regarded as northern forms. There can hardly be any ob- 

 jection made to taking Hatteras as this dividing point; for here it is, 

 let it be remembered, that the line of separation between the warm 

 along-shore current and the cold along-shore current exists. 



With these remarks as prefatory to the discussion concerning geo- 

 graphical range, a close study of the tables will now be entered upon 

 with the purpose of seeing what must have been the geographical 

 range of Pleistocene forms. Of the 160 species whose ranges are 

 known, eighty-eight have their extreme northern geographical range 

 either at Cape Hatteras or some point south thereof, and may be 

 classed as southern forms. This in itself, according to Fisher, would 

 be sufficient to stamp the Pleistocene forms of South Carolina as 

 constituting a southern facies, his law being that if more than 50 per 

 cent, of any aggregation of marine fauna belong to any one facies, 

 the whole aggregation may, in general terms, be placed under that 

 facies. Here the percentage of strictly southern forms is fifty-five. 



