A-44. 



This pattern of emergence cannot be explained without a 

 rigorous examination of the factors that control the distri- 

 bution of these organisms. 



Study of some of the ten end-members elucidates several 

 of these factors. End-member 4 is composed of two species, 

 the alcyonacean Anthomastus agassizi-t and the gorgonian 

 Parmuriaea borealis both of which are restricted to hard 

 substrates. They are dominant deeper in the northern can- 

 yons, but are not found in the southern canyons even though 

 suitable substrate (outcrops) does occur at comparable 

 depths in Norfolk Canyon. Aaanthogorgia armata (8) and 

 Desmophyllum oristagalli (9) are also restricted to hard 

 substrates. In Norfolk Canyon both of these species co- 

 occur on the same outcrops. In the northern canyons 

 Aaanthogorgia armata is most prevalent on the glacial 

 erratics occurring on the wall of Oceanographer Canyon, 

 while Desmophyllum oristagalli. is restricted to the under- 

 hangs of the more massive outcrops found in the axes of all 

 three northern canyons (Table VII) . These four species do 

 have at least one thing in common, the fact that they are 

 restricted to hard substrates and are therefore found mainly 

 in canyon areas. However, without more detailed information 

 on some of the other factors, such as current activity, the 

 specifics of these overlapping but discontinuous distribu- 

 tions cannot be interpreted. 



