8 



ALLAN HANCOCK PACIFIC EXPEDITIONS 



VOL. 27 



data of these tables are computed from figures presented in Hartman 

 (1963), assuming that the Campbell grab covers an area of 0.55 m^ and 

 the orange-peel grab 0.25 m^. The tables give trends and approxima- 

 tions rather than absolute values, because the various depth classes of 

 each canyon have not been exhaustively sampled to the point of diminish- 

 ing returns of previously unassessed variability. The abundance of 

 polychaetes and echinoderms in the canyons in depths of 0-200 m closely 

 approximates the averaged density for the coastal shelf (Table 4), but 

 mollusks are slightly less and crustaceans are much less abundant in the 

 canyons. The insular canyon sediments apparently are not significantly 

 different in grain size from those of mainland canyons, as shown by the 

 scatter diagram (Graph 1 ) of median diameters, although they appear 

 to have slightly higher carbon percentages (Graph 4) or are, at least, on 



Graph 4. Scatter diagram of axial canyon carbon percentages in 

 sediments, quoted as percent carbon direct. Symbols of canyons: 

 C == Catalina, D = Dume, H = Hueneme, J ^ La Jolla, M = Mugu, 

 N = Newport, = Coronado, R = Redondo, SM = Santa Monica, 

 SP = San Pedro sea valley, T^ Tanner, B = basin below sill 

 depth. Data from Emery and Hiilsemann (1963). 



