92 ALLAN HANCOCK PACIFIC EXPEDITIONS VOL. 27 



On the Numerical Values of Polychaete and Echinoderm Species 

 with Latitude and Distance from Shore: — The following analyses of 

 species in the canyons show the step-down effects resulting from 

 latitude and distance from shore. The kinds of species change from 

 north to south, and from inshore to offshore canyons; some species 

 drop out, others are added. Polychaetes, represented by 37 specific 

 categories in the northernmost, Monterey canyon, are increased by 69 

 species to total 91 species in Hueneme canyon; 22 are common to 

 Monterey canyon. In Mugu canyon an additional 57 species appear to 

 bring the total to 117 species; of these 22 are common to Monterey 

 canyon and 38 to Hueneme canyon. Proceeding southward, Dume canyon 

 has 70 species; of these 17 are common to Monterey canyon, 20 to 

 Hueneme, 6 to Mugu, and 27 are newly added. The same procedure 

 follows for the remaining areas, named below. 



The rise and fall in numbers is irregular, partly because the 

 sampling procedures were not the same; numbers of samples and their 

 sizes varied considerably. 



The numbers of echinoderms show a similar pattern of replacement. 

 Four species are named in Monterey canyon. Hueneme is represented 

 by 6, of which 1 is common to Monterey canyon and 5 are added. 

 Mugu canyon has 14 species of which 3 are common to Monterey, 

 and 3 to Hueneme canyon. Dume canyon has 16 species; 2 are known 

 also in Monterey, 4 in Hueneme, none in Mugu and 10 are newly 

 added. 



It should be re-emphasized that the number of species does not in- 

 crease proportionately to the number of samples taken. On the other hand, 

 the number of species increase abruptly when substrata differ. This re- 

 placement by canyon, depth, latitude and kinds of sediments can be noted 

 for every benthic species found in the canyons. 



