24 ALLAN HANCOCK PACIFIC EXPEDITIONS VOL. 27 



solenogasters and a white snail, Mitrella permodesta, and numerous 

 polychaetes occur. Echinoderms are represented by Asteronyx loveni 

 and Ophiomusium jolliensis, and crustaceans are nearly absent. Woody 

 fragments are encountered in 715 meters, with Cadulus tohniei, a 

 scaphopod, Mitrella, and a small white enteropneust with subspherical 

 proboscis. Other animals, to depths of 786 meters are Brissopsis 

 pacifica and Brisaster townsendi, siliceous sponge, polychaetes, mainly 

 Phyllochaetopterus limicolus and Protis pacifica, together with dead 

 shells of Cyclopecten. There is no life below 825 meters. 



SAN PEDRO SEA VALLEY 

 This canyon (Fig. 8) is represented by \?) grab and 2 dredged 

 samples. Volumes of grab samples ranged from a low of 0.7 cuft in 

 461 m, to 5.74 cuft in 187 m. Depths ranged from 187 to 740 m, 

 with dredged samples coming from 100-300 to 240-280 meters. 



Highest biomass values were measured in 319 m, and values 

 were high in all depths except at 406 and from 661 m downward, 

 where impoverished conditions exist. In all samples the polychaetes 

 comprised the greatest bulk and highest numbers of kinds of speci- 

 mens. Combining all samples the following kinds of animals are repre- 

 sented: polychaetes with 145 species; echinoderms with 17 species; 

 mollusks with 25 or more species ; crustaceans with 11+ species ; other 

 kinds with 15-|- species, or in all more than 220 species. 



As in other canyons, the change of specific groups with increasing 

 depth is conspicuous. About 91 species of polychaetes occur in depths 

 to 221 m. Most of them have their maximal numbers and sizes in 

 these ranges. Only a few, such as Chlocia pinnata and Maldane sarsi, 

 attain their maximum development at greater depths, except for some 

 of the typical deepwater forms below 400 meters. 



Heteroinastus filobranchus is inconspicuous in this canyon ; its 

 greatest concentration is at 406 m, but nowhere has it the abundance 

 found in the northern canyons. Capitclla capitata subspp. are not 

 abundant in any of the samples, but concentrations have been earlier 

 reported in adjacent areas (see Hartman, 1955, p. 81) ; it is possible 

 that an area of concentration does exist in an axis depth, but that it 

 was not located in the survey. 



Peak occurrences of a few species are noteworthy; they include 

 Spiophanes fimbriata, Myriochele gracilis, Sthenelanella uniformis and 

 Chloeia pinnata, all in 221 meters. Deepwater species are restricted to 



