44 ALLAN HANCOCK PACIFIC EXPEDITIONS VOL. 27 



13.6 gin/ sq.m., in 825 m. 8.8 gm/ sq.in., in 706 m. 



12.84 gm/ sq.m., in 686 m. 4.3 gm/ sq.m., in 8 10 m. 



12.6 gm/ sq.m., in 741 m. 3.8 gm/ sq.m., in 715 m. 



12.6 gm/ sq.m., in 848 m. 



In 76 meters, 241 specimens of Arnygdalum (a clam) comprised 

 the bulk of the animal weight. In 378 m the weight was due chiefly 

 to an Arhynchite, accompanied by Listriolobus in shallower depths, 

 Brissopsid urchins were heaviest in depths of 200 to 611 meters, 

 after which a seastar occurred. Mollusks at 137 meters were mainly 

 Yoldia and Dentalium. At 378 meters two polychaetes, Spiophanes 

 and Pectinaria, comprised the bulk. 



The deepest parts of Redondo canyon share the biological character- 

 istics of Santa Monica basin ; biomasses are very low and animal 

 kinds are similar to the basin. 



San Pedro sea valley: — Biomass values expressed in grams to a 

 square meter are as follows : 



234.8 gm/ sq.m., in 437 m. 1 14.0 gm/ sq.m., in 468 m. 



206.0 gm/ sq.m., in 522 m. 28.0 gm/ sq.m., in 740 m. 



194.0 gm/ sq.m., in 319 m. 27.4 gm/ sq.m., in 406 m. 



185.2 gm/ sq.m., in 459 m. 20.0 gm/ sq.m., in 666 m. 



141.4 gm/ sq.m., in 187 m. 8 gm/ sq.m., in 716 m. 



156 gm/ sq.m., in 461 m. 7.8 gm/ sq.m., in 661 m. 



Ranging these samples by major groups of animals, the following 

 kinds comprised the bulk of the weight : 



In 187 m, total weight 70.7 grams: 



polychaetes 53.75% 



mollusks, with shells 33.24 



a sipuiiculid 11.60 

 a nemertean 1.41 



In 319 meters, total weight 97.0 grams: 



5 echinoids, Brisaster 62.9% 



2 Arhynchite sp. 33.6 

 polychaetes 2.3 

 nemertean 1.0 



In 406 m, with 13.7 grams, polychaetes comprised nearly 100%. 



In 437 meters, with 58.7 grams: 



3 echinoids 85.98% 

 polychaetes 17.04 



1 Arhynchite sp. 6.98 



