NO. 2 HARTMAN: QUANTITATIVE SURVEY 289 



SAN PEDRO SLOPE 



'I'he San Pedro (SP) slope, in depths below 60 fms, is an oceanward 

 down-sloping extension of the San Pedro shelf. It is dissected by the San 

 Gabriel sea valley; near its outer limits it surrounds the Lasuen sea 

 mount and Sixmile bank. One of its greatest depths, 440 fms, is attained 

 north of Sixmile bank (no. 213 on Map, Pt. 1). Its terrain is overall 

 irregular, compared with that of adjacent areas. Surface sediments are 

 mainly silt, mud and clay, with rocky rubble and gravel in the vicinities 

 of the sea mounts. 



The fauna in the soft bottoms is diversified and patchy. Biomass 

 values at depths of 90 to 100 fms approach 100 grams to a sample; these 

 values diminish to a fraction of a gram at greatest depth, showing a more 

 or less steady decline with depth. Rocky outcrops occur in 170 and 180 

 fms near no. 174 (see Map, Pt. 1 ) , and in 240 fms at no. 197 ; these are 

 also the sites of siliceous sponge and conspicuous representatives of echi- 

 noderms ( Sta. 2987, 2416). The values of specific diversity, by increasing 

 depth, are illustrated : 



