125 



and troughs, the analysis of the feeding types of the animals living in this 

 environment is of some interest. As there were so few living species col- 

 lected, it will be difficult to give a true assessment of the dominant feeding 

 types. All of the pelecypod species are deposit feeders, the single gastropod 

 is a predator, the two echinoids are non-selective deposit feeders, the three 

 scaphopods are deposit feeders and the eight coral species are probably 

 predaceous suspension feeders. The feeding types among the shallow-water 

 dead shell species found in the deep troughs consisted entirely of sus- 

 pension and algae feeders — the dominant feeding type found on the 

 intertidal rocky shores at the edges of these channels. The California 

 Province mollusks found as dead shell in the basins consisted of 80"/o 

 deposit feeders, and \2°/q were designated suspension feeders, giving some 

 indication that they must have lived in a detritus-rich clay bottom en- 

 vironment. 



IX. Upper Slope, Central and Southern Gulf, 

 121 to 730 Meters: 

 The list of invertebrates for this environment is typical of bathyal 

 depths, and two species of mollusks found in this study, the pelecypod, 

 Nucula Cardura, and the scaphopod, Cadulus californicus, were even 

 reported from abyssal depths in a list of all known abyssal mollusks com- 

 piled by Clarke (1962). Bottom water temperatures in this portion of the 

 Gulf are normal for bathyal depths, ranging from 1 1° or 12°C. in the upper 

 parts to about 4° or 5°C. in the lower or deeper portions. Oxygen concen- 

 trations are very low at these depths in most of the Gulf (fig. 6), ranging 

 from 1 ml/L. in the shallower portions to less than .05 ml/L. in the 300 

 to 500 meter zone, increasing slightly to .5 ml/L. at depths of 700 to 800 

 meters. Very few living organisms were taken in the low-oxygen portions 

 of the upper slope, and several regions were completely devoid of life, even 

 though trawls and dredges brought up large amounts of wood and un- 

 decayed organic matter (Goldberg and Parker, 1960). The only animals 

 which could be considered at all common in this zone were several species 

 of Stomatopod shrimp (Squilla), and at times tremendous numbers of 

 Pleuroncodes planipes and Munida, both Galatheid shrimp. It is suspected 

 that all of these shrimp are probably carrion feeders and thus should find 

 food plentiful in this region where organic decay is very slow. It is of 

 interest that Vinogradov (1953) stated that both Squilla and Pleuroncodes 

 are high in phosphate content, especially in the form of the mineral, 

 apatite, the principal mineral found in phosphatized wood taken in this 



