20 ALLAN HANCOCK PACIFIC EXPEDITIONS VOL. 27 



REDOXDO CANYON 



Redondo canyon (Fig. 6) is a steep-wallcd, nearly straight, westerly 

 directed canyon about nine miles long. It intersects the shallow main- 

 land shelf of Santa Monica Bay to near shoreline and extends west- 

 ward to Santa Monica basin. Depths range from 57 to 853 meters. 

 The sediments of its sampled areas are chiefly fine grained silty, to 

 sticky green or blue or gray mud. except in some axes depths, where 

 gravels and coarse sands occur. 



This canyon has proven most interesting, perhaps because it was 

 the most completely sampled. Fifty-six samples come from all depths 

 and parts. It is here recognized for a south wall (shown as shaded 

 circles on the chart), a north wall (clear circles), axis depths (struck 

 circles), basin slope (crossed circles), and fan (circles half shaded). 

 Except in most of its lower or fan extension, where the fauna is 

 impoverished as it is in its adjacent basin, the fauna is diverse, high 

 in standing crop and indicates an availability of food and replenishing 

 larval supplies. 



Large samples have usually been recovered using either the smaller 

 orange-peel, or the larger Campbell grab, except in a few cases 

 where closure of the jaws was incomplete. Volumes were thus usually 

 between 2 to 4 cuft. Screenings retained little but living and dead 

 remains of animals, many foraminiferan tests and some mud fractions. 

 Flocculent and other debris came usually only from shallower parts, 

 and some broken shells in a few samples. 



Along the south wall mud was recovered in all but three samples; 

 one of these had sand and gravel in 76 meters, the other two had 

 flocculent debris in 232 and 519 meters. The shallowest sample had 

 high numbers of a nest-building bivalve, Amygdaluin pall'idulum, 

 and the 232 m sample contained many individuals of two kinds of 

 capitellids, H eteromastus filobranchus and Decamasius gracilis. At 519 

 meters there were peak numbers of Amphissa, a giant Scalibregma 

 inflatum, and other wormlike animals. Peak numbers of an ophiuroid, 

 Amphipholis pugetana, came from 542 meters, and Chloeia pinnata 

 with Pholo'e glabra in 57 meters, whereas Chloeia with Pectinaria 

 characterized the bottom in 378 meters. Largest individuals varied 

 with depth ; at 76 m it was a maldanid and a nemertean ; at 

 232 and 378 m an echiuroid, at 519 and 575 m a nemertean, and at 

 542 m a brissopsid. On the whole, there is a diminution in numbers 



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