2 U.S. NATIONAL MUSEUM BULLETIN 260 



by J. L. Barnard (1966a) ; and additional North Pacific records by 

 Shoemaker (1964). 



The Menzies trawl (Menzies, 1962) is designed to collect small 

 motile crustaceans and its success may be measured by the large num- 

 ber of small amphipods, many newly described, which have been col- 

 lected in so few^ samples. 



Composition of the Samples 



The eight samples wath the most numerous specimens occur in 

 depths from about 800 to about 4400 m. The recovery of various 

 familial groups is highly erratic. For instance, ampeliscids and 

 phoxocephalids are sparse or absent in samples 7234 (791 m) and 

 7230 (2706 m) but they are abundant in all samples from depths be- 

 tween these extremes. Oedicerotids and synopiids are also erratic in 

 occurrence. Several genera and species sporadically occur in dif- 

 ferent samples and 18 species of the total of 81 collected are repre- 

 sented by single specimens. Nevertheless, the number of species is 

 high in some samples, station 7229 (1748 m) yielding 38 species. 

 These facts indicate that the amphipod fauna of bathyal and upper 

 abyssal depths is rich and diverse. Many more species are expected 

 to be found in future explorations of this study area. Perhaps a 

 dozen species, which have not been described here because of their 

 fragmentary condition, occur in the samples. Oedicerotids and 

 lepechinellids particularly are subject to severe damage during wash- 

 ing of sediments after sampling. 



The number of Amphipoda per sample decreases \vith increments 

 in depth, but this may reflect to some extent the increased difficulty 

 of keeping the trawl on the bottom in great depths. 



There is virtually no relationship of the fauna recovered in the 

 Cedros Trench to that of nearby coastal shelves (see lists of species 

 in J. L. Barnard, 1964c, 1966b). Barnard (1966a) has discussed the 

 dissimilarities between bathyal faunas of submarine canyons and 

 those of the southern Calif ornian shelf. Only Pracliynella lodo, 

 Pardisynoj/ia synoflae of station 7234 (842 m) and the cui-ybathic 

 Argissa fhamati'pes of station 7229 (1748 m) occur on the deep por- 

 tions of the coastal shelf and only the genera Ainpeh'sca, Byhlis, Lem- 

 bos, Liljehorgia, Illetaphoxus, Monoculodes^ Orcliomene^ Paraphoxus^ 

 Phoxoceplialus^ and RJiachotropis have representatives on the coastal 

 shelf. Only the species of MetapTioxus and Phoxocephalus appear to 

 have any direct relationships with their sublittoral congeners, but in- 

 terspecific morphological differences in these genera are so small that 

 even these relationships are uncertain. 



