to Florida, the West Indies, and is also found in Brazil (John- 

 son 1934: Morris 1951, 1973: Abbott 1968, 1974; Emerson et 

 al. 1976). 



Corbula contractu is a common bivalve species of the 

 northwest Atlantic of which there are 22 samples containing 

 46 specimens in our collection (Table 5). 



Our samples are primarily from off New England shores. A 

 group of samples occurs on the central part of Georges Bank, 

 one off the coast of Maine, several occur in Nantucket and 

 Vineyard Sounds, and another grouping south of Nantucket 

 Shoals on the outer edge of the continental shelf (Fig. 27; 

 Theroux and Wigley footnote 4, table 43). 



The bathymetric distribution of this species ranges from 0.5 

 to 115 m (Johnson 1934; Porter 1974). 



Our samples are from water depths ranging between 15 and 

 150 m with a mean of 58 m. Forty-six percent of the samples 

 and 41% of the specimens are in the 50-99 m depth range 

 grouping, 27% of the samples and 28% of the specimens in the 

 25-49 m grouping, 13% of the samples are in the 0-24 m and 

 100-199 m groupings, specimen percentage in each of these 

 groupings is 9 and 22%, respectively (Table 268). 



This species reportedly inhabits sand and mud substrates 

 (Morris 1951). 



Our samples also came from sand and muddy substrates, 

 although the sandier substrates were preferred. Sand con- 

 tained 53% of the samples and 49% of the specimens, while 

 silty sand contained 32 and 27%, respectively. Muddy frac- 

 tions, silt and clay, contained 5% of the samples and 10% of 

 the specimens for the former and 1 1% and 15% for the latter, 

 respectively (Table 269). There are three samples containing 

 five specimens which are unclassified with regard to sediment 

 type. 



Corbula krebsiana C. B. Adams 1852. Kreb's corbula. Figure 

 28. 



It is reported to occur at Florida and the West Indies by 

 Johnson (1934) and Abbott (1974), while Andrews (1971) 

 listed it as occurring at Jamaica and Texas; Andrews further 

 stated that it is an uncommon, infaunal creature residing on 

 offshore banks. 



This species is represented by 97 specimens from 41 sam- 

 ples in the NEFC collection (Table 5). 



Samples in the NEFC collection occur on the outer con- 

 tinental shelf from Cape Hatteras-, N.C., to Miami, Fla. (Fig. 

 28; Theroux and Wigley footnote 4, table 44). 



Depth range of this species is from 5 to 156 m (Johnson 

 1934). 



Our samples range from 18 to 135 m in depth with a mean of 

 44 m. Sixty-three percent of the samples and 56% of the 

 specimens are in the 25-49 m depth range grouping, while 22% 

 of the samples and 35% of the specimens are in the 50-99 m 

 grouping. The 0-24 m grouping and the 100-199 m grouping 

 contain 10 and 5% of the samples and 6 and 3% of the speci- 

 mens, respectively (Table 270). 



Our specimens inhabited shelly and sandy substrates. Sand 

 was by far the preferred sediment type, containing 63% of the 

 samples and 59% of the specimens. Next largest amounts, 29 

 and 36% for samples and specimens, respectively, were in 

 sand-shell substrates; shell substrates contained 5 and 3%, 

 respectively, while silty sand substrates had the least with 2% 

 of the samples and 2% of the specimens (Table 271). 



Corbula sp. Figure 28. 



The NEFC collection contains one sample with two speci- 

 mens of this taxon (Table 5). 



The single sample containing the specimens of Corbula sp. 

 is from the Maine coast (Fig. 28; Theroux and Wigley footnote 

 4, table 45), at 45 m depth in a clay sediment. 



Family HIATELLIDAE 



The NEFC collection contains 17 specimens from 7 sam- 

 ples which bear the classification Hiatellidae (Table 5). 



There are two groups of samples containing members of the 

 family Hiatellidae, one group occurs north of Cape Cod in the 

 Gulf of Maine containing one sample on the Scotian Shelf and 

 two samples in the southern Gulf of Maine, one north of 

 Boston and the other east of Cape Cod. The second group 

 occurs south of Charleston, S.C., to the northern portion of 

 Florida (Fig. 49: Theroux and Wigley footnote 4, table 81). 



Our samples range in depth from 29 to 1 10 m with a mean of 

 56 m. Three depth range groupings contain members of this 

 taxon; they are the 25-49 m grouping with 57% of the samples 

 and 29% of the specimens, the 50-99 m grouping with 29% of 

 the samples and 12% of the specimens, and the 100-199 m 

 grouping with 14 and 59%, respectively (Table 272). 



Sand substrates contained 71% of samples but only 35% of 

 the specimens, while sand-gravel substrates, although con- 

 taining 14% of the samples, contained 59% of the specimens. 

 One sample (14%) containing one specimen (6%) occurred in 

 clay substrates (Table 273). 



Genus Cyrtodaria Cuvier 1800 



Cyrtodaria siliqua (Spengler 1793). Northern propeller clam. 

 Figure 40. 



This species is moderately common offshore, and occa- 

 sionally found in fish stomachs (Abbott 1974). 



The northern propeller clam is distributed from Arctic 

 Ocean regions to Cape Cod, Mass., Georges Bank, and 

 Rhode Island (Johnson 1934; La Rocque 1953; Ockelmann 

 1958; Morris 1973; Abbott 1974). 



This species is represented in our collection by two speci- 

 mens from one sample (Table 5). 



The single sample we have in our collection is from off Cape 

 Ann, Mass. (Fig. 40; Theroux and Wigley footnote 4, table 

 66). 



The reported depth range for this species is 9 to 165 m 

 (Johnson 1934; Abbott 1974). 



The sample in our collection is from 70 m of water placing it 

 in the 50-99 m depth range grouping. 



There is no information relating to sediment in our sample. 



Genus Hiatella Daudin, in Bosc 1801 



Hiatella arctica (Linne 1767). Arctic saxicave. Figure 48. 



This species is widely distributed throughout the Northern 

 Hemisphere, it ranges from Arctic seas to deep water in the 

 West Indies and off Panama; it is also found in the British 

 Isles, in the Mediterannean and Bering Seas, and in the Paci- 

 fic Ocean (Johnson 1934; La Rocque 1953; Ockelmann 1958: 

 Clarke 1962; Tebble 1966; Abbott 1968, 1974; Morris 1973). 



49 



