85 



Gastropods 

 Solariella nuda 

 Turcicula bairdii (dead) 

 Cocculina diomedae (dead) 



Lamellibranchs 

 Solemya agassizi 

 Lucinoma, sp. nov. 

 Vesicomya lepta (dead) 



Cephalopods 

 Argonauta pacifica (dead) 



Solenogasters 

 Prochaetoderma, sp. nov. 



Crustaceans 

 Benthesicymus tanneri 

 Heterocarpus affinus 



Heterocarpus, sp. nov. 

 Paracrangon areolata 

 Glyphocrangon spinulosa 

 Acanthephyra curtirostris 

 Axiopsis {Calocarides), sp. nov. 

 Munidopsis, sp. 

 Parapagurus pilasimanus 

 Neolithodes diomedae 

 Paralomis multispina 

 Paralithodes rathbuni 

 Gnathaphausia zoea 



Holothurians 

 Molpadia musculus (violaceum type) 

 Molpadia musculus {musculus type) 

 Synallactes ishikawa 



XI. Abyssal southern borderland basins, and outer 

 continental slope, 1,800 to 4,122 meters. 



The abyssal region represents a complete change from the previously 

 discussed deep-water environments, both in the diversity of fauna and the 

 great abundance of individuals. Although only 15 stations were occupied 

 at these depths, 186 species of benthic invertebrates have been identified, 

 and many more are yet to be checked by specialists. Whereas in most of 

 the shallower slope stations a species would be represented by only a few 

 individuals, the species from the abyssal regions were extremely abundant, 

 often comprising hundreds of individuals per station. The richness of 

 fauna actually approaches that of the inner continental shelf. 



Bottom-water temperatures within this environment range from 1.2° 

 to 2.6°C. (fig. 11), which can be considered characteristic of true abyssal 

 conditions. The oxygen values ranged from 1 to 2.8 ml/L., being high 

 enough to support most forms of marine life. All stations except one were 

 taken on pure silty clay bottom. The one exception was taken on clay 

 with appreciable amounts of manganese crust. This environment differs 

 from that of the middle continental slope in having lower bottom-water 

 temperatures, much higher oxygen, and occurs on a relatively level, silty 

 clay bottom, whereas the middle slope is characterized more by steep 

 rocky and sandy bottom. Only five of the 86 species from the abyssal 

 basin and slope environment were also found at middle slope stations. 

 One species, the pelecypod, Chlamys latiaurata monotimeris, lives on kelp 

 fronds, thus falls to the bottom wherever kelp drifts; one is a hermit crab, 



