NO. 2 HARTMAN : QUANTITATIVE SURVEY 219 



PALOS VERDES SHELF AND SLOPE 



The Palos Verdes shelf (PV), in depths of 7 to 10 fms, supports 

 conspicuous Chnetopterus associations consisting chiefly of this genus with 

 other kinds of polychaetes. In its shallowest part, where sediments are 

 somewhat sandy, the parchment-worm is associated with enteropneusts 

 harboring pinnotherid crabs, the large swarming nereid, Neanthes 

 brand ti, juvenile sand-dollars Dendraster excentricus, a tubicolous an- 

 nelid Rupolymnia crescentis with a commensal polynoid Ilalosydnn 

 brevisetosa, the proboscis worms, Glycera aincricana and G. robusta, and 

 small spioniform worms, especially species of Po/ydora and Prionospio. 

 At about 10 fms, the parchment-worm is associated with the case-building 

 clam Lima dehiscens, and the worms Myxicola infundibuluni and Gol- 

 fingia ?hespera ; in bottoms where rocks and gravel occur, it is present 

 with gorgonian coelenterates, Tclepsavus costnriiin and Phyllochnetop- 

 teriis prolifica. 



In depths of 11 to 20 fms, (^haeiopterus is associated with decreasing 

 numbers of Lima dehisccns and, where gravel or rocks occur, with the 

 spiny ophiuroid, Ophiothrix spicu/ata, the elbow crab, Heterocrypta 

 occidentalism the cone-snail, Conus calif ornicus, other mollusks, including 

 Nassarius, iMegasurcula, Polinices, together with large nemerteans, 

 Cerebratulus rubra, the large cageworm, Pherusa capulata, as well as 

 many other kinds of polychaetes, anemones of several kinds, and sipun- 

 culids. Red-brown sands support Sipunculus nudus, Lytechinus anamesus, 

 other ophiuroids, and many kinds of shelf-polychaetes. In depths of 14 

 to 20 fms, a sea-star, Astropecten californicus, ophiuroids, such as Amphi- 

 oplus hexacanthus, Amphipholis squamata and Amphiodia urtica, are 

 prominent, together with increasing numbers of small crustaceans and 

 polychaetes. 



In 21 to 30 fms, the sediments of the Palos Verdes shelf are black 

 muds with odor of hydrogen sulfide, flocculent black debris and decaying 

 vegetation. Animals are chiefly polychaetes, Dorvillea articulata, Amphn- 

 rete arctica, Lumbrineris pallida, other Lumbrineris species, Ophiod- 

 romus pugettensis, Boccardia basilaria, Tharyx species, Diopatra ornata, 

 and other smaller polychaetes, associated with a clam, Solemya sp., sipun- 

 culids, and Amphiodia urtica. At this depth Chaetopterus and crusta- 

 ceans are nearly absent. 



In 31 to 40 fms the animals in the sediments are mainly polychaetes, 

 especially cirratulids, spionids, some Pectinaria calif orniensis, and nemer- 

 teans, such as the large Cerebratulus ; surface forms include Chloeia 

 pinnata, Ophiothrix spiculata, and the large sea-whip, Stylatula. Crusta- 



