VII. Outer Shelf Assemblage, 66 to 126 Meters, Sand Bottom, Northern Gulf 



of California 76 



VIII. Northern Gulf Basins and Troughs Assemblage, 230 to 1500 Meters 78 



IX. Upper Slope Assemblage, Central and Southern Gulf, 121 to 730 Meters 81 



X. Middle Continental Slope Assemblage, 731-1,799 Meters 84 



XI. Abyssal Southern Borderland Basins and Outer Continental Slope 



Assemblage, 1,800 to 4,122 Meters 85 



XII. California Borderland Basins Assemblage, 1,641 to 2,358 Meters 88 



Discussion 90 



I. The Intertidal Rocky Shores 93 



II. Intertidal Sand Beaches and Sand Flats 96 



III. Low-Salinity Lagoons and Sand Flats 100 



IV. Nearshore Shelf from 1 1 to 26 Meters 102 



V. Intermediate Shelf from 27 to 65 Meters 115 



VI. Outer Shelf, 66 to 120 Meters, Southern Gulf 120 



VII. Outer Shelf, 66 to 120 Meters, Northern Gulf 122 



VIII. Northern Gulf Basins and Troughs, 230 to 1,500 Meters 123 



IX. Upper Slope, Central and Southern Gulf, 121 to 730 Meters 125 



X. Middle Continental Slope, 731 to 1,799 Meters 127 



XI. Abyssal Southern Borderland Basins and Lower Continental Slope, 1,800 



to 4,122 Meters 129 



XII. California Borderland Basins, 1,641 to 2,358 Meters 131 



Summary and Conclusions 132 



Literature Cited 135 



Appendix List of Stations 143 



Table I. List of Species, Depth Ranges, Station Occurrences and Environ- 

 ments Where Each Species Occur 149 



Table II. Supplemental List of Invertebrate Species from Various Environ- 

 ments 1 66 



Table III. Sample Devices 176 



Abstract 



A reconnaissance study of the zoogeography and ecology of ben- 

 thic invertebrates in the Gulf of California and on the continental slope 

 off west Mexico was carried out during the years 1958-1963. A series of 

 characteristic assemblages were devised for various environments found 

 in the Gulf of California, derived from both 272 biological samples and the 

 distribution of approximately 1,150 identified species of invertebrates. 

 Using a contingency matrix of common occurrences of 280 common species 

 of invertebrates, compiled by a digital computor as a basis for preliminary 

 analysis it was possible to designate 12 separate assemblages of inverte- 

 brates. These assemblages reflected distinct environmental regions of 

 uniform depth, sediment, water temperatures and oxygen concentrations. 



