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of organisms vary with greater horizontal distance and 

 reflect differences in kinds of sediments, amounts of 

 light intensities, decreasing temperature ranges and 

 perhaps other physical factors. 



Diversity resulting from cyclic (seasonal or diurnal) 

 or from meteorological changes are believed to be insig- 

 nificant in Santa Monica Bay, except in the shallowest 

 parts where bottom temperature or salinities might differ 

 from one season to another, or after prolonged rainfalls. 



One of the most striking phenomena of patchiness 

 in areas of southern California has been observed in the 

 accumulating evidence for unusual abundance of certain 

 gregarious species occurring in one, or a few, restricted 

 patches, perhaps not exceeding several square yards in- 

 extent. In Santa Monica Bay there are such beds as 

 Schizocardium (enteropneust) with commensal pinnixid 

 crabs at Zone II-6, Dentalium rectius (scaphopod) at 

 V-2, Thalassema sp* (echiuroid worm) at V-6 and V-7, 

 Pisione nr, remota (polychaete) at II-l. Glottidia 

 albida (brachiopod) occurs in many shallow areas in 

 Santa Monica Bay, but the individuals are usually small, 

 presumably immature, and few in number in any one sample. 

 Mature individuals have been found in unusual abundance 

 at only one place (Station 3410-55) off Palisades on the 

 outer side of Santa Catalina Island in 20 fathoms, 

 Myxicola sp. (polychaete) is sparse in most parts of 

 southern California, although it is to be found in shallower 



