20. 



of it being restricted to occasional patches on the east flank. 

 In Oceanographer Canyon very high abundances of Cladorhiza sp. 

 occur between 500 to 1000 meters on both flanks of the canyon. 

 They are also found in somewhat lower concentrations in the 

 same depth range within the axis of this canyon. 



Unidentified polychaete tubes were also encountered in 

 this study though no animal was ever seen protruding from 

 them. They differ from the tubes of the quill worm Hyalinoeaia 

 avtifex in that they are curved, smaller, and most frequently 

 are seen sticking out of the substrate rather than lying on 

 top of it. They are found in areas having soft silty sedi- 

 ment. The sponge Cladorhiza sp. and these polychaete tubes 

 appear to be mutually exclusive, meaning that in areas 

 where one is exceedingly common the other one is not found. 

 This is probably a reflection of their different substrate 

 preferences. In Baltimore Canyon high concentrations of 

 these tubes occur at depth exceeding 800 meters both in the 

 axis and on the walls. High concentrations of polychaete 

 tubes are found only between 800 to 1000 meters in the axis 

 of Lydonia Canyon, while decreased abundances occur shallower 

 in the axis and on the west wall. Occasionally, patches of 

 heavy concentrations of these tubes are also found on both 

 flanks of the canyon between the depths of 500 to 1000 meters. 

 The substrate variability in Lydonia Canyon allows both 

 Cladorhiza sp. and the polychaete tubes to occupy the same 



