32. 



factors govern the occurrence of these anemone beds . The 

 deeper water fauna of Baltimore Canyon is rather homogeneous, 

 with rattails and the red crab Geryon quinquedens dominating 

 the faunal assemblage. 



Principal components analysis of the fauna observed in 

 Baltimore Canyon resulted in 8 9% of variance in the data set 

 being explained by ten end-members or twelve species. Eight 

 of these end-members are monospecific, meaning that the dis- 

 tributions of these species are independent of each other and 

 of all other species in the data set. The other two end- 

 members are dispecific, being composed of two species that are 

 positively correlated in terms of their distribution. The high 

 proportion of monospecific end-members indicates that no 

 cohesive grouping (i. e. a community) of interdependent species 

 occurs throughout the canyon, meaning that dominant members 

 of the fauna are controlled by different factors. On closer 

 examination of the results of this analysis the general pattern 

 of gradual species replacement with increasing depth emerges. 



The species composing the first ten end-members, as well 

 as a plot of their occurrence in Baltimore Canyon, are shown 

 in Fig. 14. Examination of the occurrences of these end- 

 members identifies the faunal trends. The shallow-water fauna 

 is composed of six of these end-member groups (2, 3, 4, 7, 8 

 and 10) . The galatheid crab Munida valida and the starfish 

 Asterias vulgaris (10) , dominant between 100 to 200 meters. 



