NO. 5 BARNARD: AMPHIPODA 25 



parently because the oiifshore waters are more transparent and algae live 

 at greater depths than on the mainland shelf. Hence, the descent of the 

 species indicated in Table 19 may have other causes than factors asso- 

 ciated with a canyon environment. 



The ascent of bathyal species along canyon pathways cannot be de- 

 termined because of sparse data on their occurrence in normal environ- 

 ments of the slope. The shallowest known member of the bathyal fauna 

 is Harpiniopsis fulgens, recorded at 128 m but extending to depths of 

 2000 m. This great eurybathicity suggests, however, the probability that 

 the species normally occurs in shallow depths. Other harpinias do 

 not occur in depths shallower than 300 m. The deep-sea species of Am- 

 pelisca, Byblis, Liljeborgia and Leptophoxus do not ascend to depths 

 shallower than 400 m in these latitudes. 



Amphipod ecologists must note the unusual association of Ampelisca 

 lohata and Paraphoxus abronius with plants, the former being espe- 

 cially associated with intertidal surfgrass, perhaps inhabiting the in- 

 terstices at the root level, and the latter almost always being associated 

 with samples bearing masses of red algae (whether or not attached to 

 the substratum is not known) . 



The genus Listriella represents an interesting case that is linked to 

 the Listriolobus situation. Mills (1962b) has published evidence that a 

 species of Listriella on the Atlantic coast of America is a commensal 

 with polychaetes, especially maldanids. In southern California Listriella 

 is particularly associated with the Listriolobus community wherein 

 maldanid polychaetes also are predominant. Three of the five species, 

 Listriella albina, L. goleta and L. eriopisa, are confined primarily to 

 fine-silt beds bearing Listriolobus and each species declines in frequency 

 toward the edge of the coastal shelf, but is rather prominent in canyon 

 samples. Listriella albina notably has a second area of maximum den- 

 sity in the canyons in depths of 300 to 400 m (Table 20). Host-specific 

 association between most listriellas and maldanids is not apparent in 

 data of either canyons or the Listriolobus bed, although Listriella albina 

 is strongly associated with Maldane sarsi. Generally, samples con- 

 taining any maldanids have several genera and species. At least 18 spe- 

 cies of maldanids in 13 genera have been recovered in the canyons and 

 two or more species of Listriella usually occur in maldanid samples. 

 Occasionally samples having Listriella do not have maldanids. A 

 single maldanid, Axiothella rubrocincta (see Barnard, 1964 and Reish, 

 1963), inhabits Bahia de San Quintin but it is not associated with 



