190 ALLAN HANCOCK PACIFIC EXPEDITIONS VOL. 19 



SUMMARY OF RESULTS 



A sampler lowered almost anywhere off the coast of southern Califor- 

 nia recovers an amazing array of kinds of animals. These kinds and 

 numbers vary from one sample to the next and attain large numbers in 

 shallow bottoms. This diversity extends not only to most samples and in 

 all kinds of sediments, but throughout the year, with little indication of 

 season. It is difficult to relocate the exact spot from which a sample was 

 taken, except in shallowest bottoms or in few places where one or few 

 species are known to occur in massed numbers. Such are some known 

 Dendraster and Capitella bottoms, where exceptional aggregates occur. 

 Usually the numbers of species in a sample from shallow bottoms range 

 to a hundred or more, with individuals numbering to near five thousand. 

 These species occur as aggregates, where the presence of one generally 

 indicates that of other kinds ; they seem to maintain their restricted 

 locations over periods of years, as proven by subsequent probes in suc- 

 cessive seasons and years. 



The kinds of species and their respective numbers, the stages of devel- 

 opment, and the state of maturity, as well as the associations with other 

 groups in the sample, are repetitive characteristics and should therefore 

 be predictable. 



Samples with large numbers of specimens are generally characterized 

 by having one or a few species with exceptionally high numbers of indi- 

 viduals ; these specific units may change from one sample to the next, and 

 their occurrences are not as predictable as are the aggregated species with 

 which they occur. Their kinds and distributions are indicated by an aster- 

 isk in the charts, below. Exception must be made for the Amphiodia 

 urtica-Pectinaria californiensis association, in which individual numbers 

 continue high along most of the edge of the San Pedro shelf and in other 

 areas remote from shore, especially where sediments are somewhat impov- 

 erished. Isolated peak numbers are indicated for many of the more than 

 600 species named below. Peak numbers may be partly explained by the 

 successful establishment of spatfalls of larvae, but they do not explain the 

 continuance of the colony through successive generations. 



Specific diversity in southern California is so characteristic that large- 

 scale communities of organisms cannot be identified. Exception may be 

 made for a Listriolobus pelodes colony on the Santa Barbara shelf (Bar- 

 nard and Hartman, 1959) where a continuous shelf depth is occupied by 

 an identifiable community of organisms. 



Numbers of species and specimens are highest in shelf depths, and 

 lowest in outer slopes and the oxygen-impoverished, long-shore basin 



