NO. 2 OLGA hartman: submarine canyons 13 



pallida, Onuphis vexillaria, Spiophanes fimbriata, a thalassemid echiu- 

 roid, Arhynchite, or Nephtys and Pectinaria, the last two where sedi- 

 ments are sandy. A sample from 456 m, in gray mud with sand, 

 pebbles and some gravel, had significant numbers of Capitella, an indi- 

 cator of upset salinity conditions, and the deepest sample, in 621 m, 

 in gray sand, is impoverished or nearly dead. 



The numbers of species and specimens from shallowest to deepest 

 parts show variation, but the change in values may express differences 

 due to kinds of sediments, with mud having generally the highest, 

 and sand to gravel the lowest values. At greatest depths the sediments 

 are increasingly silty and contain conspicuous amounts of black, oval 

 fecal pellets, chiefly those of Heteromastus filobranchus (see Emery 

 and Hiilsemann, 1962, p. 170). The large burrowing echiuroid worm, 

 Arhynchite sp., is most abundant and largest in 373 and 376 m; it 

 exists in sediments having many fecal pellets which are cylindrical 

 and slightly annular, differing in these respects from those of Hetero- 

 mastus, which are elongate oval, 



Tubicolous worms in Hueneme canyon include (1) Pectinaria 

 calif orniensis, inhabiting a slender, cone-shaped tube, and most con- 

 centrated in depths of 338 to 376 m, where individuals number to 

 200 in a sample; (2) Nothria iridescens inhabiting a clay-covered, 

 cylindrical tube and attaining highest numbers in 376 and 397 meters; 

 (3) Nothria pallida constructing a muddy (to sticky mud) tube and 

 attaining peak numbers in 209 and 373 m; (4) Onuphis vexillaria 

 occupying a similar but larger tube and most abundant at 373 m. 

 Onuphid tubes are internally lined with a white chitinized layer and 

 thus distinguishable from those of (5) Pista disjuncta, which is most 

 frequent in depths of 209 and 383 m. (6) Spiophanes fimbriata 

 attains peak numbers in 576 m; it inhabits a thin-walled, copper- 

 colored, silt-covered tube. 



The brackish capitellid, Capitella capitata subspp., was found in con- 

 centration at only one depth, 456 m, in sediments of sand, mud, 

 pebbles and gravel. 



Brissopsid urchins, chiefly Brisaster townsendi, are first present 

 at 209 m ; they increase in size and number at 383 m to 9 specimens 

 per sample, weighing 217.5 grams, and again at 478 m, where 6 

 weigh 126 grams. A large shelled clam, Cyathodonta pedroana, com- 

 prises the bulk of the weight, in 271 and 228 m. At its lowest 



