Our samples are from the edge of the continental shelf off 

 the eastern tip of Long Island, N.Y. (Fig. 61; Theroux and 

 Wigley footnote 4, table 107). 



The Arctic wedge clam occupies the Arctic, Boreal, and 

 Virginian zoogeographic provinces (Coomans 1962); Gosner 

 (1971) placed it only in the Boreal province, while Dance 

 (1974) placed it in the Arctic, Boreal, and Transatlantic pro- 

 vinces. 



Depths occupied by this species range from low water to 

 approximately 92 m (Abbott 1968, 1974). 



Our two samples are from 93 and 99 m water depths. This 

 depth range places both samples in the 50-99 m depth range 

 grouping (Table 208). 



Morris (1951), Abbott (1968), and Emerson et al. (1976) 

 reported that this species is normally found in sand sub- 

 strates. 



Our samples occurred in silty sand which contained 50% of 

 the samples and 4% of the specimens, and clay with 50% of 

 the samples and 96% of the specimens (Table 209). 



Family SOLENIDAE 



The NEFC Specimen Reference Collection contains 39 

 specimens of bivalves from 1 1 samples which were classified 

 only to the familial level of Solenidae (Table 5). 



One sample containing members of this family is from east 

 of Nantucket Shoals in the Great South Channel area, another 

 from the continental shelf off the entrance to Delaware Bay. 

 the remainder are from around Cape Hatteras, N.C., extend- 

 ing from the mouth of Chesapeake Bay to south of Cape Fear, 

 N.C. (Fig. 102; Theroux and Wigley footnote 4, table 181). 



Samples containing members of the family Solenidae range 

 in depth from 13 to 53 m with a mean of 26 m. The majority of 

 these samples are in the 0-24 m depth range grouping which 

 contains 64% of the samples and 36% of the specimens, while 

 the 25-49 m grouping contains 27% of the samples and 26% of 

 the specimens; the 50-99 m grouping contains the smallest 

 amount of samples, 9%, but the greatest number of speci- 

 mens, 39% (Table 210). 



Samples containing members of the family Solenidae were 

 found in four different sediment types: gravel, sand-shell, 

 sand, and silty sand. Sand sediments contained the majority 

 of both samples and specimens, 50% for the former and 63% 

 for the latter; sand-shell substrates contained 30% of the 

 samples and 21% of the specimens: silty sand contained 10% 

 of the samples and 13% of the specimens, while gravel sub- 

 strates contained 10% of the samples and 4% of the specimens 

 (Table 211). There is 1 sample containing 15 specimens which 

 is unclassified with regard to sediment type. 



Genus Ensis Schumacher 1817 



Ensis directus (Conrad 1843). Atlantic jackknife clam. Figure 

 43. 



This species is distributed from the Gulf of St. Lawrence 

 and Newfoundland, along the whole U.S. Atlantic coast, 

 south to Florida (Johnson 1934; Morris 1951, 1973;LaRocque 

 1953; Ockelmann 1958; Abbott 1968, 1974). 



Ensis directus is a very common bivalve of the northwest 

 Atlantic whose commonness is reflected in our Specimen 

 Reference Collection which contains 2.150 specimens from 



206 samples, each accounting for 2% of their respective cate- 

 gory for the entire sampling suite (Table 5). 



Our samples are distributed from the Northeast Peak of 

 Georges Bank ranging along the entire continental shelf south 

 to just north of Miami, Fla. (Fig. 43; Theroux and Wigley 

 footnote 4, table 71). 



This species inhabits the Boreal. Virginian, and Carolinian 

 zoogeographic provinces (Coomans 1962); Gosner (1971) 

 placed it in the Boreal and Virginian provinces, while Dance 

 (1974) placed it in the Boreal, in east North America, and the 

 Transatlantic provinces. 



This species bathymetric habits are principally littoral and 

 intertidal but does extend down to approximately 37 m in 

 depth (Morris 1973; Porter 1974). 



Our samples are from depths which range between 1 and 

 100 m with a mean of 31 m. The majority of samples are in the 

 shallowest depth range grouping 0-24 m which contains 45% 

 of the samples and 67% of the specimens; there is a gradual 

 decline in abundance with increasing depth range with 38% of 

 the samples and 30% of the specimens occurring in the 25-49 

 m depth range grouping; 17 and 3%, respectively, in the 50-99 

 m grouping and traces occurring in the 100-199 m grouping 

 (Table 212). 



The Atlantic jackknife clam is commonly found on sandy 

 mud or sand bottom near the low water mark (Abbott 1968, 

 1974). 



In our collection 70% of the samples and 60% of the speci- 

 mens occurred in sand, 20% of the samples and 13% of the 

 specimens occurred in sand-shell, and between 1 and 3% of 

 the samples and < 1 to 2% of the specimens occurred in 

 gravel, sand-gravel, shell, silty sand, and silt substrates 

 (Table 213). There are 12 samples containing 37 specimens 

 which are unclassified with regard to sediment type. 



Genus Siliqua Megerle 1811 

 Siliqua costata Say 1822. Atlantic razor clam. Figure 99. 



The Atlantic razor clam is distributed from eastern portions 

 of Canada, the Gulf of St. Lawrence, and Newfoundland 

 south to North Carolina (Johnson 1934; La Rocque 1953; 

 Ockelmann 1958; Abbott 1968, 1974; Morris 1973, Emerson et 

 al. 1976). 



Siliqua costata is a common northwestern Atlantic bivalve, 

 the NEFC Specimen Reference Collection contains 104 

 specimens of this species from 32 samples (Table 5). 



The NEFC samples are primarily from the Georges Bank 

 region with a few inshore collections in the New England 

 region (Fig. 99; Theroux and Wigley footnote 4, table 176). 



Coomans (1962) and Gosner (1971) reported this species an 

 an inhabitant of the Boreal and Virginian provinces, while 

 Dance (1974) listed it as occupying the Arctic and Boreal 

 provinces in eastern North America as well as the Transatlan- 

 tic province. 



This species is primarily a shallow water inhabitant but 

 does range out to approximately 29 m depth (Abbott 1974; 

 Porter 1974). 



Our samples are from water depths which range between 8 

 and 260 m with a mean of 55 m. The majority of the samples 

 occurred in mid-shelf depths and shallower. In terms of depth 

 range groupings, 47% of the samples and 39% of the speci- 

 mens are in the 50-99 m depth range grouping, while 31% of 



39 



