26 ALLAN HANCOCK PACIFIC EXPEDITIONS VOL. 27 



Listriella melanica. On the other hand, the amphipod is strongly cor- 

 related* with Pista alta (Terebellidae), suggesting that listriellas may 

 also live in association with polychaetes of families other than Maldan- 

 idae. 



Depth Distribution of the Amphipoda in the 

 Canyons and Basins 



The known depth distributions of those species collected in the sub- 

 marine canyons and basins have been arranged in Table 18. Extreme 

 depths and mid-depths are quoted. The species are arranged in groups 

 depending on their occurrence in shallowest water depth and in each 

 group according to their greatest depth penetration. 



Only four species are restricted to water of less than 30 m in depth. 

 The next group of species has minimum depths of less than 20 m, but 

 occurs from 82 to 1941 m in maximum depth. There follows a group of 

 species with minimum ranges of 21-100 m and then progressively 

 groups of species with minimum depth extremes of 100, 200, 300, 400 

 m, etc. 



The largest group of species has its minimum depths between and 



20 m, but there is a surprisingly high percentage of the taxa demon- 

 strating rather strong penetration to greater depths. Of the 64 species 

 (Graph 12 and Table 21) occurring in waters of 0-40 m, only 13 are 

 restricted to depths shallower than 100 m and 11 extend to depths ex- 

 ceeding 500 m. A similar situation occurs in that group of species hav- 

 ing minimum depths between 40 and 100 m (Graph 12). Only 3 of the 



21 species are confined to waters of less than 100 m and 8 occur in 

 depths greater than 500 m. 



Knowledge of the bathymetric ranges of species confined to depths 

 exceeding 300 m is more imperfect than of those known from less, be- 

 cause the distributions of the shallow water species are based on more 

 than 400 shelf and upper slope samples that supplement the samples 

 taken from the canyons and basins. 



Potentially, almost all of the coastal shelf species known in depths 

 of 200 m or less might be found in the submarine canyons, at least in their 

 shoreward parts. In this study, 92 species having depth ranges of 0-200 

 m on the shelf have been collected in the canyons, although 185 species 

 are known to occur on the shelf in those depths. The density of sam- 

 pling in the canyons has not approached that on the shelf, and probably 



*r = 0.43253+, N = 91. 



