FISHERY BULLETIN: VOL. 71, NO. 1 



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Figure 5. — Geographic distribution of skeletal remains of the echinoderms Brisaster fragilis and Strongylocen- 



trotus drobachiensis. 



Figure 6. — Bathymetric range and mean depth of oc- 

 currence of echinoderm remains. (Mean values are 

 listed in Table 3.) 



shallow waters of Nantucket Shoals and the 

 other four were in moderate to deep water near 

 the shelf break (Figure 5). Bathymetric range 

 at the locations where this species was found 

 was from 38 to 201 m (Table 3, Figure 6). 



REMAINS OF MOLLUSKS 



Remains of mollusks were among the most 

 common organic seabed constituents. In total 

 abundance they ranked second ; only the echi- 

 noderms were more plentiful. Four major groups 

 of mollusks were represented in the material 

 analyzed. Pelecypods were the most abundant 



molluscan group, gastropods ranked second, and 

 the cephalopods and scaphopods were present 

 in relatively small quantities. These groups are 

 discussed below in the order of their abundance. 



PELECYPODS 



Pelecypod shells were abundant and conspic- 

 uous components of the prefossil animal re- 

 mains. In addition to their relatively large size, 

 often the color and texture of the shell surface 

 contrasted sharply with the sediments in which 

 they occurred. Size of the shells ranged from 

 such large, robust species as Spisula solidissima 

 (12 cm), Arctica islandica (10 cm), and Placo- 

 pecten magellaniciis (10 cm) , to such small, frag- 

 ile forms as Thyasira gouldi, Nucula proxima, 

 Bathyarca pectuvadoides, and others, all of 

 which were 5 mm or less. A total of 57 species 

 representing 40 genera were collected. Typical 

 species are illustrated in Figure 7. Pelecypod 

 remains were very widespread; they were col- 

 lected at all stations except three (3, 47, and 62) . 



8 



