NO. 2 HARTMAN : QUANTITATIVE SURVEY 191 



(Hartinan and Barnard, 1958, p. 29). Numbers of species and specimens 

 have ranged to 88 species and about 4500 specimens per sample. 



Biomasses are highest in long-shore areas, especially the Palos Verdes 

 and San Pedro shelves, where the sediments are enriched by the runoff of 

 the mainland. Single samples have yielded a gross moist weight of 768 

 grams per sample, and similar high biomasses have been found on the 

 San Pedro shelf and other places along the shelflands of southern Cali- 

 fornia (see California, 1965a, 1965b, pp. 104-319). 



Most of the species named below may be expected to produce individ- 

 uals with a short life span, not exceeding a year. Cursory examinations 

 have shown that ova are usually numerous in mature individuals, insuring 

 the wide dispersal of larval stages, well beyond the limits in which the 

 species normally settles and matures. Nearly all can be expected to occur 

 in competition with others, where space, food, protection from predators 

 are factors determining survival and further reproduction. The fact 

 remains that most of the benthic stages of these species continue to exist 

 only in selected places. It must be assumed that these areas are previously 

 biologically conditioned by the predecessors of the same species. 



This horizontal distributional pattern is closely linked to that of ver- 

 tical zonation, for it can be seen (see charts) that replacement of closely 

 related species, by depth, is a constant factor of these benthic animals. 

 The result is a stepping-stone effect, where greater depths result in a 

 dropping out of many species, and additions of others. This effect is illus- 

 trated not only for the polychaetes, but for echinoderms and mollusks, 

 and may extend to other well represented groups. It has also been demon- 

 strated for the faunas in the submarine canyons of southern California 

 (Hartman, 1963a). 



ACKNOWLEDGEMENTS 



Many scientists from the Allan Hancock Foundation of the Uni- 

 versity of Southern California participated in various aspects of this 

 study. The collections of samples were taken aboard the Research Vessel 

 VELERO IV, and processed aboard ship by members of the Hancock 

 staff. The tedious tasks of sorting and identifying the thousands of speci- 

 mens were performed by numerous specialists and assistants ; to them 

 much gratitude is due for their patience and care. These assistants were 

 supported by the Allan Hancock Foundation, the California State Water 

 Pollution Control Board, and the National Science Foundation; the 

 administrations of these organizations are gratefully recognized for their 

 cooperation. T he identifications of invertebrate specimens were under- 

 taken by various specialists (see Bibliography at end). The echinoderms 



