2 PROCEEDINGS OF THE NATIONAL MUSEUM vol. 119 



G. F. Jones, aboard the 'R\ jVelero IV, was instrumental in collecting 

 and processing the samples. Captain Fred C. Ziesenhenne identified 

 the ophiuroids dominating the bottom samples. Dr. Joel W. Hedg- 

 peth of Pacific Marine Station loaned specimens of a new species of 

 Protomedeia. The Beaudette Foundation and the Smithsonian In- 

 stitution supported the project and the National Science Foundation 

 provided funds for illustration (grant G-10750). 



Methods and Data 



The benthos of Monterey Bay, in water depths of 15 to 116 m 

 (table 1) is represented by those 46 samples charted in figure 1. They 

 are relatively evenly distributed in proportion to bathymetry. The 

 coastal benthos of southern Cahfornia is represented by 348 samples 

 evenly proportioned to depths between 10 and 200 m. The two 

 groups of samples, although disparate, are roughly proportional in 

 number to their respective bottom areas. Any comparisons between 

 the Amphipoda of the two areas must be viewed with caution. 



Samples of sediment and fauna were collected with an orange- 

 peel grab taking a surface area of 0.25 m^. Barnard and Jones (1960) 

 have considered the average mechanical efficiency of the grab to be 

 about 80 percent if large numbers of samples are taken on diverse 

 substrates. The efiiciency decreases on hard-packed sand bottoms 

 and increases on soft silty bottoms. Calculations of frequencies of 

 Amphipoda in the 348 southern Cahfornia samples employed the 80 

 percent efficiency rule. Those of Monterey Bay employed a 100 

 percent efficiency rule. All sedimentary samples from Monterey 

 Bay, with one exception, exceeded 1.5 m^, the mark of 100 percent 

 efficiency. Presumably differences in depth of penetration of the 

 grab in those samples of 100 percent areal efficiency would not affect 

 tallies of Amphipoda except for those listriellas inhabiting deep 

 burrows of polychaetes and echiuroids. 



Sedimentary samples were washed through meshes of 0.7 mm 

 square openings and the residues preserved in a mixture of seawater 

 and formaldehyde. Amphipoda and those other animals considered 

 to be dominants in the samples were removed to alcohol in the labora- 

 tory. The remaining materials were represerved and stored in the 

 collections of the Allan Hancock Foundation. Thorson's (1957) 

 methods were used to determine standing-crop dominance. 



Planning and conducting of the surveys were based on USHO 

 charts contoured in EngHsh fathoms, but the bathymetric data have 

 been converted to meters herein. Hence the depth classifications of 

 benthic areas in southern California, quoted in meters, are not in 

 standard intervals of 10, 20, 30 m, etc., but are in converted intervals 

 of 10, 20, 30, etc., fms. 



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