144 ALLAN HANCOCK PACIFIC EXPEDITIONS VOL. 19 



SUMMARY OF RESULTS 



The unscreened samples have shown that much of the bottom of San 

 Pedro Basin is bed rock overlain by silt, ooze, clay or fine detritus in a 

 layer that exceeds in thickness the depth of the grabbing devices. Most 

 of the samples have been of this kind. Some have come up with varying 

 amounts of rock, gravel, or rubbly materials. Such are samples from the 

 vicinities of submerged mounts, on either side of the northwestern and 

 southeastern threshholds (see chart 2, and sample 235, above). Large 

 rocks come from parts of Redondo Canyon (sample 12b), from a canyon 

 southwest of Newport Bay (121a), and from steep slopes off the eastern 

 end of Catalina Island (241, 252, and 267). Pleistocene gravel comes 

 from a canyon wall (at 125) and blackened phosphorite rocks from 

 sample 52. 



It is noteworthy that samples taken with uniform methods, using the 

 orange-peel grab, have been very irregular in volumetric amounts, rang- 

 ing from as much as 3.71 cu. ft. in a sample (39), to as little as a quart 

 (0.033 cu. ft.) in another (267a). These differences are explained in 

 several ways. For 252, 262, and 263, the grab closed before the bottom 

 had been penetrated, perhaps through an oversensitivity on the part of the 

 trigger, or from striking a swimming object, such as a large fish. For 

 some samples (45b, 241b, and 267a), the jaws were incompletely closed 

 on ascent, due to the presence of rocks and debris. For others (65, 66a, 

 and others) the hard packed bottoms of sand, clay or other materials, 

 could not be penetrated by the device used. Furthermore, it was not 

 possible to measure the amounts of the sample which might have filtered 

 out on hauling up the grab, or to retrieve the solid particles, including 

 animals, which might have escaped through apertures, such as vents for 

 releasing water pressures. In spite of unmeasurable losses of varying 

 amounts, the quantities and diversities of the samples are conspicuous. 



Most of the bottoms of San Pedro Basin have been found to support 

 a rich and varied fauna in shallow to great depths, except for a con- 

 spicuous impoverished area in the western end (see chart 2, and text, 

 below). The diversity is manifested not only in single samples, where the 

 numbers of species may run very high, but in samples from adjacent areas, 

 indicating a patchiness of occurrence which is unpredictable, and at 

 present unexplainable. 



