NO. 2 HARTMAN, BARNARD: BENTHIC FAUNA OF DEEP BASINS 225 



RELATIONSHIP OF BASIN FAUNAS TO THE COASTAL 



SHELF 



About half the species occupying basin floors normally live on the 

 coastal shelf in depths of 120 meters or less (Table 3). The three 

 shallower nearshore basins have a higher percentage of shelf species, 

 68%, than three of the deepest offshore basins, which have only 46% 

 of shelf species. The farthest basin, Tanner, of intermediate depth, has 

 a surprising number of shelf species, 60%. 



Despite these remarkably high percentages of shelf species in the 

 basins, the number of extremely eurybathic species on the coastal shelf 

 is low. Thus, in the Polychaeta, Echinodermata, and Crustacea, there 

 are 1106 species on the coastal shelf, of which 96 or 8.7% are eury- 

 bathic and descend into the basin faunas. Many of the remaining 1010 

 species are eurybathic to the extent of descending onto the coastal 

 slopes below 200 meters, but not into the basins. 



The Polychaeta and Crustacea common to five or more of the basins 

 number 24, of which 67% are shelf species (Table 4). 



Table 3. Specific shelf component of Basin faunas, utilizing only Poly- 

 chaeta, Crustacea, and Echinodermata, specifically known. 



