NO. 2 OLGA HARTMAN : SUBMARINE CANYONS 11 



the sediments are dark gray silt and support chiefly large individuals 

 of a bamboo-worm, Asychis disparidentata, a large enteropneust and 

 a capitellid, HeteroiJiastus filobranchus. In 260 m, in dark gray silt, 

 the largest animals are an echiuroid, Arhynchite sp. with 23 specimens, 

 4 large echinoids, Brisaster townsendi, and smaller animals of many 

 kinds of polychaetes, crustaceans, mollusks, ophiuroids and sipunculids. 

 In 410 meters, in olive green silt with many dead shells of Dentalium 

 and Ainphissa, the largest individuals are Arhynchite and Brisaster, 

 accompanied by many kinds of polychaetes, some mollusks and sipuncu- 

 lids. In 750 meters, in coarse gray sand, the screenings contain much 

 woody and flocculent debris; the animals are small and of few kinds, 

 including amphipods and cumaceans in large numbers, and polychaetes 

 of the genera Capitella and Nephtys, with little else. 



HUENEME CANYON 



This canyon (see Fig. 2) was sampled in depths of 98 to 621 

 meters, from axis and walls. Size of samples varied from a low of 

 1.29 to a high of 5.16 cuft. The sediments were gray, green or black 

 mud and silty gray sand, ranging to coarse gray sand with mud, olive 

 green silty sand, and gray muddy sand with pebbles or gravel. 



In the shallowest sampled depth, at 98 m, the bottom axis sedi- 

 ments are coarse gray sand with flocculent debris and black algal 

 strands. Numbers of animal species run high and specimens are 

 moderately small, with none conspicuous. In 165 meters the sediments 

 are gray sand with tubes of Pectinaria. The largest animal is Glycera 

 americana, associated with high numbers of Haploscoloplos elongatus. 

 In 177 m the bottom sediments are green to black medium sand; 

 they support the tubicolous Asychis disparidentata and burrowing worms, 

 chiefly Listriolobus pelodes and Heteromastus filobranchus. This depth 

 supports the largest number of species (38) and specimens (677) recorded 

 in Hueneme canyon. 



The most conspicuous kinds of animals in muds in shallow (to 

 200 m) depths are worms: Heteromastus filobranchus, Asychis, Gly- 

 cera, Travisia, Pista disjuncta, Listriolobus and Cerebratulus, all 

 selecting silty mud. Haploscoloplos and Pectinaria are most abundant 

 in sandier sediments. In greater (373 to 478 m) depths large bris- 

 sopsid echinoids, first Brisaster, then Brissopsis, occur with a scaph- 

 opod mollusk, Dentalium rectius, two clams, Yoldia scissurata and 

 Cyathodonta pedroana, together with tubicolous polychaetes Nothria 



