21. 



depth interval, but again they are rarely found in the same 

 area. The polychaete tubes were never found in high concen- 

 trations in Oceanographer Canyon. 



The other type of organism for which quantification was 

 not obtained is a small colonial hydroid. Previous observa- 

 tions made from a submersible indicate that these hydroid 

 colonies inhabit substrates consisting of a thin veneer of 

 silt overlying a hard crust. Many of these hydroids were 

 obtained during the dredging in Baltimore Canyon, but no 

 large concentrations were seen during the photographic survey 

 of that canyon. In Lydonia Canyon these colonial hydroids 

 are found in several patches on the walls of the canyon. 

 The highest concentrations of hydroid colonies are found 

 along the west wall of the axis of Oceanographer Canyon 

 between the depths of 500 to 800 meters, with occasional 

 sparse patches in other areas. 



Faunal density 



The density of epibenthic fauna varies with depth. 

 Figure 5 shows the faunal density with respect to depth for 

 the three canyons combined. Densities are high in the shallow 

 depths with a peak between 300 to 400 meters. A second peak 

 occurs between 1700 - 1800 meters. Between 600 to 1500 meters 

 densities are uniformly low. The high faunal density between 

 300 to 400 meters was mostly the result of high concentrations 

 of the quill worm Hyalinoeoia avtifex and small encrusting 



