The NEFC samples are from depths which range between 6 

 and 50 m with a mean of 26 m. The 25-49 m depth range 

 grouping contains the majority of both samples (52%), and 

 specimens (68%); next most plentiful amounts of samples and 

 specimens are in the 0-24 m grouping which contains 45% of 

 the samples and 30% of the specimens, while the deepest 

 grouping in which they are grouped, 50-99 m, contains 3% of 

 the samples and 3% of the specimens (Table 238). 



Boss (1972), in his monograph on the family Semelidae, 

 reported that this species is normally found in offshore sandy 

 substrates. 



Our samples occurred in shell, which contained 2% of the 

 samples and 0.7% of the specimens, sand-shell with 27% of 

 the samples and 23% of the specimens; the majority occurred 

 in sand, which contained 66% of the samples and 59% of the 

 specimens, while silty sand substrates contained 5% of the 

 samples and 17% of the specimens (Table 239). 



Semele purpurascens (Gmelin 1791). Purplish semele. Figure 

 98. 



The purplish semele is distributed from North Carolina to 

 Florida and the Gulf of Mexico, it occurs in the West Indies, 

 and is also found at Uruguay and Brazil along the South 

 American coast (Johnson 1934; Abbott 1968, 1974; Boss 1972: 

 Morris 1973; Emerson et al. 1976). 



Semele purpurascens is fairly common, however, the 

 NEFC collection contains only six specimens from four sam- 

 ples (Table 5). 



Our samples are from the continental shelf with one sample 

 occurring off the Cape Hatteras, N.C., coast, another off 

 Charleston, S.C.. and another slightly north of Miami, Fla. 

 (Fig. 98; Theroux and Wigley footnote 4. table 174). 



This species has a fairly wide bathymetric range, occurring 

 in water depths which range from ± 1 to 130 m (Abbott 1968: 

 Porter 1974). 



The NEFC samples are from water depths which range 

 between 30 and 80 m with a mean of 59 m. The 25-49 m and 

 50-99 m depth range groupings contain 25 and 75% of the 

 samples, and 33 and 67% of the specimens, respectively 

 (Table 240). 



Boss (1972) reported that this species is normally found in 

 sandy substrates. 



Our samples were found in sand-gravel, sand-shell, and 

 sand. Sand-gravel substrates contained 50% of the samples 

 and 50% of the specimens: sand-shell contained 25% of the 

 samples as did sand, but 17% of the specimens occurred in 

 sand-shell and 33% in sand (Table 241). 



Semele sp. Figure 98. 



The NEFC Specimen Reference Collection contains three 

 specimens from two samples which are classified to the gener- 

 ic level Semele sp. (Table 5). 



The samples bearing this designation are from the continen- 

 tal shelf off the central section of the Florida Peninsula (Fig. 

 98; Theroux and Wigley footnote 4. table 175). 



The samples are from water depths of 20 and 22 m. These 

 depths place both samples in the 0-24 m depth range grouping. 



One of our samples containing two specimens (68%), 

 occurred in shell, while the other sample occurred in sand- 

 shell and contained 32% of the specimens. 



Family SOLECURTIDAE 

 Genus Tagelus Gray 1847 



Tagelus plebeius (Lightfoot 1786). Stout tagelus. Figure 103. 



This species is distributed from Cape Cod, Mass., to Flor- 

 ida and Texas and other Gulf States, it is also present in the 

 West Indies and has been found in Brazil (Abbott 1968, 1974; 

 Morris 1973; Emerson et al. 1976). 



Tagelus plebeius, which is moderately common to locally 

 abundant throughout its range, is represented in the NEFC 

 collection by four specimens from one sample (Table 5). 



Our sample is from the western slope of Cape Cod, Mass., 

 in Buzzards Bay (Fig. 103; Theroux and Wigley footnote 4, 

 table 184). 



Coomans (1962) placed the distribution of this species in the 

 Virginian, Carolinian, and Caribbean provinces. 



The stout tagelus is normally an intertidal inhabitant and 

 ranges down to approximately 8 m depth (Abbott 1968, 1974). 



Our sample is from a water depth of 1 m placing it in the 0-24 

 m depth range grouping. The bottom sediment was sand- 

 gravel. 



Family ARCTICIDAE 



Genus Arctica Schumacher 1817 



Artica islandica (Linne 1767). Ocean quahog. Figure 8. 



Arctica islandica (formerly Cyprina islandica) is a commer- 

 cially important bivalve of the northeastern United States 

 with landings in 1978 totalling 23 million pounds of meats, an 

 increase of 22% over the 1977 landings (Pileggi and Thompson 

 1979). 



In the western Atlantic the ocean quahog ranges from the 

 Arctic Ocean and Newfoundland to off Cape Hatteras, N.C. 

 (Johnson 1934); La Rocque (1953), Abbott (1974), Morris 

 (1973), and Emerson et al. (1976) listed it as also occurring at 

 Iceland. In the eastern Atlantic, Tebble (1966) reported it 

 from the British Isles, Iceland, the Faroes, Onega Bay in the 

 White Sea, and the Bay of Biscay. 



The ocean quahog occurs in 3.6% of our samples and repre- 

 sents 1 .9% of the specimens in the collection (Table 5). It must 

 be remembered, however, that these samples represent only 

 material presently on hand in the Specimen Reference Collec- 

 tion and not the complete list of records concerning this 

 species at the NEFC. 



Our samples of this species range from Nova Scotia to Cape 

 Hatteras. N.C. (Fig. 8; Theroux and Wigley footnote 4. table 

 13). The only embayment in which we found specimens was 

 Cape Cod Bay, all other samples were confined to more 

 offshore regions. 



The zoogeographic distribution of the ocean quahog is Arc- 

 tic. Boreal, and Virginian in the western Atlantic and Celtic in 

 Europe (Coomans 1962): Gosner (1971) assigned it to the 

 Boreal and Virginian provinces, and Dance (1974) to the 

 Arctic. Boreal, and Transatlantic. 



Reported water depths for this species range from 9 to 165 

 m (Johnson 1934; Abbott 1974). Clarke (1962) reported a 

 depth of 1,094 m, but stated that this needs further confirma- 

 tion. 



Our samples range in depth from 10 to 400 m with a mean 

 depth of 79 m. Fifty-seven percent of samples and specimens 



44 



