NO. 1 HARTMAN, BARNARD: BENTHIC FAUNA OF DEEP BASINS 11 



Screenings have shown consistently the presence of many translucent, 

 brassy colored, limp, nonannulated tubes, resembling long plant stems, 

 which are the tube remains of the chaetopterid. Along with them there 

 are usually few to many white calcareous, slender tube fragments of 

 Protis ; they are seen frequently as tracings on dead shells of Cyclopecten, 

 their relationship having been described by Hartman (1955b). A photo- 

 graph (Plate 1, fig. 1) of the bottom shows irregularities at the surface 

 due largely to the projecting, irregularly strewn tubes of Phyllochaetop- 

 terus. The finer screenings consist largely of subspherical and discoid 

 shells of foraminiferans, which may have their existence in the water 

 masses overlying the basin. 



The three major species of the basin, mentioned above, have their 

 more extensive distributions at the sills or on the deep slopes bordering 

 the San Pedro Basin, where they attain greater size and become sexually 

 mature. The great accumulations of dead tubes in the basin suggest that 

 these species might once have existed as reproductive stages ; on the other 

 hand they may represent the accumulation of vegetative individuals over 

 many years, since there are few, if any, corroding factors to destroy the 

 tubes. 



The middle and deeper parts of the basin are more impoverished 

 than parts near the margins and the sill (Table 2). This impoverished 

 area can be delineated by a contour near the 837 meter depth, about 100 

 meters below the sill depth. 



The greatest occurrence of animals is along the rim bordering Santa 

 Catalina Island (Samples numbered 192, 193, 211, 212, 213 and 143 in 

 Hartman, 1955a) and off Point Fermin (numbered 96 and 119) (see 

 Appendix III for additional data). These margins are populated by a 

 siliceous sponge-ampharetid association which has its greatest densities at 

 the bases of submarine mounts on either side of the sills and along the 

 walls of canyons. 



The fauna of Santa Monica Basin. Santa Monica Basin is a con- 

 tinuation of San Pedro Basin (Chart 1). Its sill depth is 737 meters and 

 its bottom depth 938 meters. The temperature of the subsill water is 

 5.05° C. Its overall bottom surface area is several times that of San Pedro 

 Basin and its biological productivity considerably lower, especially in its 

 deeper central, northern and western extremities. The sediments retained 

 from 17 samples have consistently shown few animal remains, but they 

 are like those of San Pedro Basin (Appendix III) except that many 

 samples contain small gray sticks. Typical screenings are white subspheri- 

 cal or disklike foraminiferan shells, dead tubes of Phyllochaetopterus and 

 small bits of white Protis tubes, and also fragments of Cyclopecten. 



