abundant member, at least in terms of specimens, of the 

 NEFC Specimen Reference Collection which contains 12,091 

 specimens representing 11.1% of the entire collection; the 

 specimens were obtained from 223 samples which represent 

 2% of the total number of samples in the collection (Table 5). 



Our samples range nearly the entire length of the east coast 

 continental shelf, beginning at the Scotian Shelf thence south 

 to Jacksonville, Fla. (Fig. 72; Theroux and Wigley footnote 4, 

 table 124). 



The zoogeographic distribution of this species is Boreal. 

 Virginian, and Carolinian (Coomans 1962): Gosner (1971) 

 placed it in the Virginian province. 



The Atlantic nut clam is quite widely distributed with re- 

 gard to depth, ranging from approximately 1 to 805 m depth 

 (Johnson 1934; Porter 1974). 



The NEFC collection samples range in depth from 1 to 260 

 m with a mean of 48 m. Two depth range groupings vie for 

 precedence in abundance of this organism; the 0-24 m depth 

 range grouping contains 31% of the samples and 47% of the 

 specimens, while the 50-99 m grouping contains 37% of the 

 samples and 45% of the specimens: the 25-49 m grouping 

 contains 27% of the samples and 7% of the specimens, while 

 the 100-199 m grouping contains 5% of the samples and 0.8% 

 of the specimens; the 200-499 m depth range grouping con- 

 tains 0.9% of the samples and < 0. 1% of the specimens (Table 

 10). There are 2 samples containing 18 specimens which do 

 not have any depth information in their sampling data. 



The Atlantic nut clam occupied all sediment types consid- 

 ered in this report in varying proportions. The majority of 

 both samples and specimens occurred in sand substrates 

 where 48% of the samples and 40% of the specimens were 

 obtained: silty sand contained 17% of the samples and 33% of 

 the specimens and clay contained 15% of the former and 22% 

 of the latter. The abundance in the other sediment types, 

 gravel, till, shell, sand-shell, and silt ranged from 10% to < 

 0.5% of the samples; silt contained < 4% of the specimens, all 

 of the others contained < 1% of the specimens (Table 11). 

 There are 9 samples containing 32 specimens which are un- 

 classified with regard to sediment type. 



Nucula tenuis Montagu 1808. Smooth nut clam. Figure 73. 



The smooth nut clam is widely distributed, being known 

 from all Arctic seas and occurring in the North Atlantic as 

 well as North Pacific Oceans. In the Atlantic it ranges from 

 Labrador to Florida, also occurring at Greenland and in 

 northern Europe, there it ranges south to Gibraltar and possi- 

 bly into the Mediterranean; in the Pacific it ranges from Arctic 

 seas to as far south as northern Japan and to Baja, California 

 (Johnson 1934; Morris 1951, 1973; La Rocque 1953; Ockel- 

 mann 1958; Clarke 1962; Tebble 1966; Abbott 1974). 



Nucula tenuis is a common small bivalve which is repre- 

 sented in the NEFC collection by 2 ,03 1 specimens, represent- 

 ing 2% of the total number of specimens, from 215 samples 

 which also represent 2% of the total number of samples (Table 

 5). 



The NEFC samples occupy nearly the whole of the Gulf of 

 Maine, the periphery of Georges Bank, ranging onto the 

 continental shelf area in the Mid-Atlantic Bight region be- 

 tween Cap Cod, Mass., and Cape Hatteras, N.C. (Fig. 73; 

 Theroux and Wigley footnote 4. table 125). 



Ockelmann (1958) considered its distribution to be panarc- 

 tic-boreal and stated that it is circumpolar; Coomans (1962) 



placed it in the Boreal, Virginian, and Celtic provinces, while 

 Gosner (1971) placed it in the Boreal and Virginian provinces; 

 Dance (1974) placed it in the Arctic, Boreal, Californian, 

 Mediterranean, and Japonic provinces. 



Nucula tenuis enjoys a widespread bathy metric range, 

 occupying water depths from slightly offshore to rather deep 

 water, ranging from 4 to 2,297 m (Clarke 1962). 



The NEFC suite of samples ranges in depth between 16 and 

 2,365 m with a mean of 320 m. There were members of the 

 smooth nut clam occupying all of the depth range groupings 

 used in this report; however, two mid to outer continental 

 shelf depth range groupings contain the majority of both 

 samples and specimens. Forty-one percent of the samples are 

 in the 100-199 m grouping and 24% of the samples are in the 

 50-99 m grouping while specimen abundance is greatest in the 

 50-99 m grouping with 55%, and 24% occurs in the 100-199 m 

 grouping. Significantly smaller amounts occur in the other 

 depth range groupings. The 0-24 m grouping contains 0.5% of 

 the samples and < 0.1% of the specimens; 8% of the samples 

 and 4% of the specimens are in the 25-49 m grouping; there is 

 8% of the samples in the 200-499 m and 500-999 m groupings 

 which contain 3 and 5%, respectively, for specimens; the 

 1 ,000- 1 ,999 m depth range grouping contains 9% of the sam- 

 ples and 1 0% of the specimens ; the 2 ,000-3 ,999 m depth range 

 grouping contains 1% of the samples and 0.4% of the speci- 

 mens (Table 12). 



As with depth, the smooth nut clam occurred in all sedi- 

 ment types considered in this report. The distribution of both 

 samples and specimens with decreasing particle size is as 

 follows: 3% of the samples and 0.5% of the specimens oc- 

 curred in gravel; sand-gravel contained 6% of the samples and 

 4% of the specimens; till substrates 3 and 0.8%, respectively; 

 shell. 1% of the samples and 1% of the specimens; sand-shell. 

 0.5% of the samples and 0.1% of the specimens: sand sub- 

 strates contained 18 and 8%, respectively; silty sand, which 

 contained the greatest abundance, yielded 36 and 36%, re- 

 spectively, while silt contained 16% of the samples and 20% of 

 the specimens; the finest substrate, clay, contained 18% of 

 the samples and 29% of the specimens (Table 13). There are 15 

 samples containing 75 specimens which are unclassified with 

 regard to sediment type. 



Nucula sp. Figure 74. 



There are 961 specimens from 108 samples in the NEFC 

 collection which bear the designation Nucula sp. . members of 

 the nut shell group (Table 5). 



The distribution of samples containing members of this 

 taxon of primarily deep water organisms ranges from off 

 Nova Scotia south to Florida; however, there is one grouping 

 of samples in the Gulf of Maine and the inshore waters of the 

 Cape Cod region, and another off the Georgia Coast which are 

 decidedly more inshore than the majority of samples (Fig. 74; 

 Theroux and Wigley footnote 4. table 126). 



The depth distribution for this taxon in the NEFC collec- 

 tion ranges from 13 to 2.722 m with a mean of 896 m. In terms 

 of depth range groupings the majority of both samples and 

 specimens follow the geographic distribution in that they 

 occur in the 1 .000- 1 .999 m grouping which contains 28% of the 

 samples and 38% of the specimens. In terms of increasing 

 depth range grouping the distribution of samples and speci- 

 mens is as follows: the 0-24 m depth range grouping contains 



