10 ALLAN HANCOCK PACIFIC EXPEDITIONS VOL. 22 



THE NEAR SHORE BASINS: 

 SANTA BARBARA, SAN PEDRO, SANTA MONICA 



San Pedro and Santa Monica Basins are more or less continuous and 

 share the same physical and biological characteristics. The bottom sedi- 

 ments are fine dark green, of sticky to silty consistency, and subsill waters 

 contain little dissolved oxygen. Temperatures at the bottom are about 

 5.05-5.06° C. Both have an impoverished to dead bottom (Hartman, 

 1955a), with few or no living animals in the deepest and largest parts 

 of their areas. In San Pedro Basin the screenings from the samples nearly 

 always contain many dead tubes of two kinds of polychaetes (Phyllo- 

 chaetopterus and Protis) and fragments of a translucent scallop, Cyclo- 

 pecten. Dark brown, amorphous waxy lumps of various sizes are typical- 

 ly retained. The undisturbed bottom appears irregular (Plate 1, fig. 1) 

 because of the presence of many Phyllochaetopterus tubes strewn in dis- 

 orderly arrangement; they may represent the accumulations of many 

 years. Retained in the screens of 1 mm mesh are the dead tests of many 

 disklike and subspherical foraminiferans resembling those in the Santa 

 Monica Basin. In the latter, the sediments from the deepest or middle 

 part frequently contain many small sticks or small bits of wood. The 

 dead area of Santa Monica Basin is believed to be greater than that of 

 San Pedro Basin, since it comprises a much larger subsill area (Chart 1). 



The fauna of Santa Barbara Basin. Because its sill is shallow, the 

 bottom temperature of Santa Barbara Basin is higher than that of any 

 other basin. Five samples taken from scattered parts of this area have 

 yielded screenings which differ grossly from those of other basins, but 

 are much alike among themselves. They consist of the dead shells of a 

 small pteropod Spiratella, fewer white shells of a Macoma and Cardita, 

 delicate shells of pteropods Clio and Cavolina, and only scattered fora- 

 miniferan tests. Living animals are sparse but characteristic. A larger 

 clam Lucinoma, a deep water snail Nitidella, a solenogaster which may 

 differ from those found in other basins, and small polychaetes, especially 

 paraonids, are most frequent. 



The fauna of San Pedro Basin. San Pedro Basin has been sampled 

 throughout its extent at two mile intervals (Hartman, 1955a), resulting 

 in 70 quantitative samples from subsill depths (Appendix III). Its sedi- 

 ments have been found to support a very sparse or impoverished fauna, 

 with two species of polychaetes (Phyllochaetopterus unknown sp., a 

 chaetopterid, and Protis pacifica Moore, a serpulid) most abundant, and 

 the dead shell remains of a scallop (Cyclopecten sp.) most characteristic. 



