36 



Pisione nr remota many at II -1 

 Prionospio nr malmgreni 120+ at II -2 

 Prionospio pinnata 40 at I SW-6 



Ophiuroid echinoderms with peaks of productivity 

 and location: 



Amphiodia ( Amphispina ) urtica 654 individuals at 



I W-ll| 441 at I W-9; 328 at I SW-9; 141 at I SW-8; 



123 at I W-7; 118 at I NW-8; and 46 at I W-16 



Amphiodia ( Amphispina ) digitata 531 at I W-10 



47 at III-ll; and 37 at I W-13« 



Amphipholis squamata 305 at I W-11; 176 at I SW-8; 



157 at I W-10 I 126 at I SW-9 j and 78 at III-ll. 



Amphiacantha amphacantha 24 at V-4 



Ophoithrix spiculata a thick mat with hundreds of 



individuals in a sample off Whites Point. 



Bio-index is an expression of the ratio of number of 

 species to that of individuals. It varies with kind of 

 bottom and with depth. In shallow areas it is lowest 

 in mixed bottoms where currents prevail (as at Whites 

 Point) J or in Santa Monica Bay in Zone II. It rises 

 sharply with depth to Zone VI where the ratio approaches 

 one. 



In Santa Monica Bay there is a marked decrease in 

 numbers of species with increasing depth. They may drop 

 from 60 or 90 species in a shallow sample from 60 feet. 



