NO, 2 OLGA HARTMAN: SUBMARINE CANYONS 33 



In this, as in all other canyons, there is a decrease in numbers 

 and kinds with depth. The lowest part is nearly dead and the sediments 

 contain empty tubes of Phyllochaetopterus limicolus^ as in Santa 

 Monica basin but in sparser numbers, and the dead shell remains are 

 mainly those of Delectopecten instead of Cyclopecten. Most of the 

 polychaetes recorded are different from those in longshore canyons 

 and the same applies to the kinds of other animals. The Santa Cruz 

 basin (Hartman and Barnard, 1960, p. 274) supports at least 60 

 species of invertebrate metazoans of which 28 are polychaetes, 6 

 amphipods, 3 isopods, 4 echinoderms, 6 or more mollusks and 4 are 

 other kinds. 



CATALINA CANYON 



Eleven large samples (Fig. 14) come from depths of 88 to 1272 

 meters and vary in size from 2.44 to 5.52 cuft. Polychaetes ranked 

 highest specifically and numerically. Unusual concentrations included 

 Anobothrus gracilis with 565 specimens in 559 meters, Armnotrypane 

 aulogaster with 8 in 362 m, Aricidea, nr suecica with 154 in 914 

 meters, Pectinaria calif orniensis with 118 in 379 m and Haploscoloplos 

 elongatus with 44 at 379 and 559 meters. Maldane and Melinnaj two 

 deepwater genera, were most abundant in 379 meters, and Califia calida 

 in 549 and 559 meters. 



Among the echinoderms A?nphiodia urtica with 606 and Amphi- 

 pholis squamata with 105 specimens were most numerous in 88 meters. 

 Ophiomusium jolliensis with 13 and Amphiura diomedeae with 24 are 

 best represented in 559 meters. Brissopsid urchins are sparse but 

 present. Among the mollusks, Dacrydiu?7i pacificum with 44 paired 

 shells (some may be dead) are most abundant at 549 meters. Other 

 large individuals include Molpadia intermedia, Arhynchite, a nemertean 

 and Travisia pupa. 



SAN CLEMENTE RIFT VALLEY 

 This canyon (Fig. 15) was very imperfectly sampled because its 

 sampled walls are rocky and its axes depths are gravelly. Four samples, 

 all small, yielded less than a cuft of sediment with hard rocks. Animals 

 were sparsely attached to their surfaces. Biomasses are negligible for 

 this reason. The kinds of animals show affinities with those reported 

 from the San Clemente basin (Hartman, 1960, p. 274). The analyses 

 (See APPENDIX) list 21 additional species associated with hard 

 substrata. All are deepwater species, not found in longshore canyons. 



