130 



the deep coastal basins are beneath major upweHing areas, with their 

 high surface production and associated great accummulation of bottom 

 organic matter. Continental shelves along the west coast of the Americas 

 are very narrow and, because the continental slope drops off very sharply, 

 numerous slumps and turbidity currents occur which transport shelf 

 organic debris to abyssal depths. 



It was hypothesized by Parker (1961) that the competition and 

 evolution of many new forms during the early Tertiary forced many of 

 the older forms of animal life deeper down into the newly-formed trenches 

 and borderland basins which were as yet unoccupied by present-day 

 animal life. It is suspected that present day forms were absent from these 

 great depths at that time, because recent geological and geophysical 

 evidence suggests that many of the present deep ocean basins are rela- 

 tively young, and most of the major trenches of the world are thought to 

 have been formed only since early Tertiary times (Parker, 1961). The 

 major abyssal plains of the central Pacific are still comparatively devoid 

 of animal life (Filatova and Levenstein, 1961; and Agassiz, 1905), 

 which may also be related to the virtually barren surface waters over these 

 basins. The relative youth of the trenches is substantiated by the fact 

 that each trench seems to have its own endemic fauna (Zenkevitch and 

 BiRSTEiN, 1960), most of which have evolved either from Tertiary shallow 

 water forms, or have differentiated rather recently from older animals 

 which had already migrated on to the continental slope prior to the 

 Tertiary. 



In Wolff's (1961) paper on the description of the animals from one 

 Galathea station (716) off Costa Rica in 3,570 meters depth, he lists 

 54 species of invertebrates. From a composite of stations taken in equiv- 

 alent depths between Baja California and Guatemala during this study, 

 86 invertebrate species have been identified (pages 186-87). A number of 

 faunal groups were identified in Wolff's paper, but were not identified 

 in this study and vice-versa. Although sponges, actinarians, polychaetes, 

 asteroids and ophiuroids (identified in Wolff's paper) were taken in 

 large numbers in this study, most have not yet been identified by specialists. 

 Likewise, Wolff has not yet received identifications for brachiopods and 

 soft corals which were identified in the present list. Only twelve species 

 of invertebrates were taken in common by both sampling programs, of 

 which five were mollusks, two pycnogonids, two holothurians, oneophiuroid 

 and two echinoids. Wolff reports one species of fish from Station 716 

 and indicates that other species were also taken. Fish were abundant in 

 the present samples, most of which have been identified by Carl L. Hubbs 

 and Richard Rosenblatt of Scripps Institution. Other descriptions of 



