10 



ALLAN HANCOCK PACIFIC EXPEDITIONS 



VOL. 27 





4> 







«o 







•V. 



3: 



<»> 





-«: 

 o 



<: 



Pec t/n aria californiensis 

 Maldane sarsi 

 Capitella capitata 

 Chloeia pinnata 

 Pista disjunct a 

 Dent a Hum rectius 

 Heteromastus filobranchus 

 Ancis t rosy II is ten taculata 

 Spiophanes fimbriatus 

 Notftria iridescens 



Graph 5. Codominant frequency of most often occurring dominants 

 in the submarine canyons. Single cumulative domination is shown 

 for each species in each square at the right edge. 



the remaining 3 1 samples are poor in diversity and total specimens, many 

 being deep-water samples in which low diversity is to be expected. They 

 might be assignable to the Lysippe zone if one were to accept the Thorson 

 rule that only half of the samples of a community require the presence 

 of a major dominant. Many are characterized by Califia calida and some 

 by various species of Aricidea. 



In five of the nine associations, Pectinaria is a major dominant, but 

 whether those associations should be coalesced as a megacommunity or 

 segregated is a matter for consideration when more exploration of the 

 world's benthic communities and slope depths has occurred. The co- 

 occurrence of Pectinaria with either Capitella or Ancistrosyllis results 

 in high frequency values for Pectinaria, but its occurrence with Dental- 

 ium results in low values. Both Pectinaria and Dentalium live in hard 

 conical tubes and Pectinaria may be affected either spatially or biologi- 

 cally by the presence of Dentalium. 



The associations are not indelibly fixed, as Barnard and Ziesenhenne 

 (1961) have pointed out in the gradation of the Amphiodia shelf- 



