Composition and Distribution of Macrobenthic Invertebrate Fauna 



115 



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MOLLUSCA 



Figure 99 



Geographic distribution of Mollusca: A — number of specimens per square 

 bottom; B — biomass in grains per square meter of bottom. 



meter of 



or less. On Georges Bank, Georges Slope, and the South- 

 ern New England Slope their density averaged 0.1 to 

 0.6/m , and their weight averaged 0.01 g/m or less. 



Frequency of occurrence was relatively high ( 1 to 

 24%) considering the small quantities that were present 

 (Tahle 10). This high frequency of occurrence is simply 

 a reflection of their small size and wide dispersion. 

 Individuals were especially small in the Georges Slope 



area and relatively larger in the Southern New England 

 Shelf area. 



Bathymetric Distribution 



Polyplacophorans were present at depths from 16 to 

 2,840 m. They were more abundant in shallow and 

 moderate depths than in very deep water (Table 11; 

 Fig. 107). Average density in depth classes less than 500 



