The distribution of our samples is widespread throughout 

 the northern reaches of the study area extending from Nova 

 Scotia and overspreading the entire Gulf of Maine-Georges 

 Bank complex. It ranges onto the Southern New England 

 shelf area and into the Middle Atlantic Bight south to Cape 

 Hatteras, N.C.; one sample occurs on the continental shelf 

 southeast of Charleston, S.C. (Fig. 23; Theroux and Wigley 

 footnote 4. table 36). 



This species inhabits the Boreal and Virginian provinces 

 (Coomans 1 962 ; Gosner 1971); Dance ( 1 974) assigned it to the 

 Boreal province in the eastern and western North American 

 sectors and also the Transatlantic province. 



The reported depth range for this species is 6 to 260 m 

 (Abbott 1968; Porter 1974). 



Our samples range in depth from to 1 ,865 m with a mean of 

 95 m. The majority of samples (44%) and 35% of the speci- 

 mens are in the 50-99 m depth range grouping; distribution of 

 samples on either side of this range grouping decrease with 

 both increasing and decreasing depth range; the largest num- 

 ber of specimens (40%) is in the 0-24 m range grouping (Table 

 196). 



Specimens of the northern dwarf cockle occurred in all 

 sediment types. Largest quantities of samples (44%) and 

 specimens (58%) were found in sand: significantly smaller 

 quantities occurred in each of the other sediment types (Table 

 197). There are 64 samples containing 1.497 specimens which 

 are unclassified with regard to sediment type. 



Genus Clinocardium Keen 1936 



Clinocardium ciliatum (Fabricius 1780). Iceland cockle. Figure 



27. 



This species is circumboreal and circumpolar, occurring in 

 both the Atlantic and Pacific Oceans in Arctic and subarctic 

 regions. Published reports list it as occurring from Arctic seas 

 south to Cape Cod in the Atlantic and from the Arctic Ocean 

 to Puget Sound and Japan in the North Pacific (Johnson 1934; 

 Clench and Smith 1944; Morris 1951, 1973; La Rocque 1953; 

 Ockelmann 1958; Abbott 1968, 1974). 



The Iceland cockle is a very common Arctic and subarctic 

 bivalve which is especially abundant in offshore waters from 

 Maine northward. There are six specimens of this species 

 from four samples in the NEFC collection (Table 5). 



The four samples in the NEFC collection are restricted to 

 the continental shelf in the Gulf of Maine, ranging from near- 

 shore Nova Scotia and along the coast of Maine, south to 

 Cape Cod, Mass. (Fig. 27; Theroux and Wigley footnote 4, 

 table 42). 



The zoogeographic distribution of this species is Arctic 

 (Ockelmann 1958). 



Reported depth range for this species is from 6 to 183 m in 

 Atlantic waters (Abbott 1968, 1974; Gosner 1971; Morris 

 1973). Ockelman (1958). in his study of Arctic regions, re- 

 ported it as ranging from 2 to 677 m. He further stated that 

 dead shells are commonly found in the Norwegian Sea down 

 to 2,465 m. 



Our samples range from 5 1 to 1 14 m in depth with a mean of 

 79 m. Seventy-five percent of the samples and 83% of the 

 specimens are in the 50-99 m depth range grouping, while 25% 

 of samples and 17% of specimens are in the 100-199 m depth 

 range grouping (Table 198). 



Our samples were found in three sediment types. One-third 

 of the samples and 25% of the specimens occurred in gravel; 

 33% of the samples and 50% of the specimens occurred in till; 

 the remaining 33% of samples occurred in clay which con- 

 tained 25% of the specimens (Table 199). One sample which 

 contained two specimens is unclassified with regard to sedi- 

 ment type. 



Genus Laevicardium Swainson 1840 



Laevicardium mortoni (Conrad 1830). Morton's egg cockle. 

 Figure 50. 



This species is distributed from Nova Scotia to Florida, and 

 ranges into the Gulf of Mexico to Texas and south to Brazil 

 and Guatemala (Johnson 1934; Clench and Smith 1944; Mor- 

 ris 1951, 1973; La Rocque 1953; Abbott 1968, 1974; Emerson 

 et al. 1976). Ockelmann (1958) reported it from Newfound- 

 land to Cape Cod, Mass. 



This small cockle, which is especially common in the 

 Southern New England area, is represented by 104 specimens 

 from 47 samples in the NEFC collection (Table 5). 



The samples in the NEFC collection occur in two distinct 

 groupings, one of which is in the Cape Cod region and the 

 other beginning south of Cape Hatteras, N.C., on the con- 

 tinental shelf, extending south to slightly below Jacksonville, 

 Fla. (Fig. 50; Theroux and Wigley footnote 4, table 82). 



The zoogeographic distribution of Morton's egg cockle, 

 according to Coomans (1962), is Virginian, Caribbean, and 

 Celtic; Gosner (1971) placed it in the Virginian province. 



Morton's egg cockle commonly occurs from the low tide 

 zone to 8 m depth (Abbott 1968; Porter 1974). 



Our samples are from to 50 m depth with a mean of 9 m. 

 Forty-nine percent of the samples and 57% of the specimens 

 are in the 0-24 m depth range grouping, 47% of the samples 

 and 39% of the specimens are in the 25-49 m grouping, and 

 only 4% of the samples and 4% of the specimens are in the 

 deeper water, 50-99m, depth range grouping (Table 200). 



This species occupies muddy bottoms (Emerson et al. 

 1976). 



The NEFC samples were obtained in four sediment types. 

 The majority of the samples (56%) and specimens (59%) 

 occurred in sand substrates with next greatest quantities, 33% 

 for samples and 28% for specimens, occurring in sand-shell; 

 silty sand substrates contained 6% of the samples and 9% of 

 the specimens, while sand-gravel substrates contained 6 and 

 4%, respectively (Table 201). There are 1 1 samples containing 

 28 specimens which are unclassified with regard to sediment 

 type. 



Genus Nemocardium Meek 1876 



Nemocardium peramabUe (Dall 1881). Eastern microcockle. 

 Figure 70. 



The eastern microcockle occurs from Rhode Island to the 

 Gulf of Mexico, and the West Indies on to Brazil (Johnson 

 1934; Morris 1973; Abbott 1974). 



Nemocardium peramabile, which is very commonly 

 dredged off eastern Florida (Abbott 1974), is represented in 

 our collection by only two specimens from one sample (Table 

 5). 



36 



