20 ALLAN HANCOCK PACIFIC EXPEDITIONS VOL. 27 



sample belonging to both Maldane and Pectinaria-Chloeia types, an- 

 other overlap being shown between Heteromastus and Pectinaria- 

 Chloeia. 



THE BORDERLAND BASINS 



The borderland of southern California has 13 enclosed basins (Hart- 

 man and Barnard, 1958, 1960; Emery, 1960), in which 165 benthic 

 biological samples have been obtained, nearly half of which were col- 

 lected in San Pedro Basin (Table 7). Hartman and Barnard have al- 

 ready discussed the fauna of these basins, but at that time a number of 

 the amphipods had not been identified. 



Subsill waters of the nearshore basins of Santa Barbara, Santa Mon- 

 ica and San Pedro have very low dissolved oxygen values (0.2-0.3 

 ml/L) and the faunas are impoverished, the number of amphipods aver- 

 agmg only l.S/m^. In the deeper offshore basins the oxygen values are 

 higher (0.4-2.0 ml/L) and the number of amphipods per square meter 

 is 6.0, but the small number of samples and low density does not permit 

 assessment of more than a fraction of the probable amphipod fauna. It 

 will be necessary to utilize benthic trawls with fine-mesh nets to collect 

 all of the very rare species before a complete knowledge of the fauna is 

 reached. Nevertheless, the present samples give us valuable indications 

 of the kinds of abundant species (Table 8) . 



The basins support 28 identifiable species and a number of others 

 (Appendix II) that have not been identified because of fragmentation of 

 specimens. Only 7 of the 28 species are unique, so far, to the basins 

 (Table 9), the remainder having been found above sill depths, primarily 

 m the submarine canyons (because most slope sampling has been done in 

 that environment) . 



The shallowest basins (San Pedro, Santa Monica, Santa Barbara), 

 with low dissolved oxygen and low densities of animals, support a rather 

 large proportion of eurybathic organisms. Of the 9 species of amphipods, 

 5 are primarily deep sublittoral species: Ampelisca pugetica, A. mac- 

 rocephala, Heterophoxus oculatus, Monoculodes norvegicus and Urothoe 

 varvarini. Heterophoxus oculatus is truly a eurybathic organism and the 

 others are of cold-temperate occurrence. The remaining four species are 

 among the most abundant in the canyons: Ampelisca coeca, Harpiniopsis 

 epistomata, Liljeborgia cota and Byblis barbarensis. 



The next group, Santa Catalina, Santa Cruz, San Nicolas and Tan- 

 ner Basms, supports only Heterophoxus oculatus and Urothoe varvarini 

 of the deep sublittoral group, but the deep sublittoral and shallow bath- 



