NO. 2 OLGA HARTMAN : SUBMARINE CANYONS 99 



On the whole the highest values are in those canyons that were 

 best sampled ; for example, Redondo and Newport canyons are high, 

 whereas San Clemente, Tanner, Monterey and San Diego canyons 

 are low. It can be seen that specific diversification is almost as great 

 in offshore, as in longshore canyons. 



CHARACTERISTICS OF ANIMALS IN THE 

 SUBMARINE CANYONS 



Benthic animals in shelf depths or heads of canyons near shore 

 are mainly shelf species which have their more extended distribution 

 in depths of less than 100 meters. Many are highly ornamented with 

 spines, lobes, elaborate branchial processes and other epithelial proces- 

 ses. They occur in tremendous numbers and diversity, and range in 

 size from large to small. They vary according to location and to the 

 sediments they occupy. In deeper parts of canyons, where sediments 

 are chiefly mud, most of the animals are burrowing or tubicolous, 

 and soft bodied. They exist in tubes or burrows, or move freely 

 through the sediments. A few have thin shells or fragile calcareous 

 skeletons. Their surface structures tend to be smooth and their shape 

 orbicular or spherical or cylindrical. Some of the typical canyon animals 

 are illustrated in the photographs numbered Figures 17 and 18. 



Phylogenctic groups best represented in canyons are polychaetes, 

 echinoid and ophiuroid echinoderms, pelecypod mollusks, solenogaster 

 mollusks, echiuroid worms, holothurian echinoderms, enteropneusts, 

 and some small crustaceans (amphipods, isopods). Some species are 

 found throughout most of the canyons, in a wide range of depths; 

 such are Chloeia pinnata, Goniada hrunnea, Pectinaria calif orniensis, 

 paranoids, Prionospio species and others. Other species are limited to 

 shallowest, to median or to deepest parts of canyons. Still others are 

 limited to outer or southernmost canyons. The replacement of shelf to 

 slope species varies with canyon and may be partly, but not wholly, 

 dependent on kinds of sediments. The Analyses give more precise data. 



It is assumed that many of the mud dwelling species are deposit 

 feeders; others, such as nemerteans and coelenterates, are perhaps 

 predators, and some of the pelecypods may be filter-feeders. The fecal 

 pellets of Heteromastus filobranchus (Fig. 19) leave no doubt that 

 this is a deposit feeder. Others of this kind are most of the polychaetes, 

 and perhaps the echiuroids. 



