Our samples are from the Georges Bank region, and also 

 the Cape Cod region (Fig. 56; Theroux and Wigley footnote 4, 

 table 96). 



With regard to its zoogeographic distribution La Rocque 

 (1953) considered it circumboreal; Ockelmann (1958) and 

 Clarke (1962) considered it panarctic and circumpolar while 

 Gosner (1971) placed it in the Boreal province. 



The depth range for this species is 24 to 2,440 m (Johnson 

 1934; Clarke 1962). 



Our samples are from water depths ranging between 1 and 

 426 m with a mean of 57 m. The 0-24 m and the 25-49 m depth 

 range groupings contain 29% of the samples and 21 and 25% of 

 the specimens, respectively; the 50-99 m grouping contains 

 the majority of samples (38%) as well as the majority of 

 specimens (53%); only one other depth range grouping con- 

 tains members of this taxon, the 200-499 m grouping, with 5% 

 of the samples and 1% of the specimens (Table 288). 



The majority of our samples (60%) as well as specimens 

 (67%) were found in sand; sand-gravel contained 20% of the 

 samples and 20% of the specimens while sOty sand and silt 

 substrates each contained 10% of the samples and 5 and 8%, 

 respectively, of specimens (Table 289). One sample contain- 

 ing five specimens is unclassified with regard to sediment 

 type. 



Lyonsia hyalina (Conrad 1830). I0 Glassy lyonsia. Figure 57. 



The geographic range is from the Gulf of St. Lawrence to 

 Texas (Johnson 1934; Morris 1951, 1973; La Rocque 1953; 

 Ockelmann 1958; Abbott 1968, 1974; Emerson et al. 1976). 



Lyonsia hyalina is common in the Northern Hemisphere, 

 the NEFC collection contains 544 specimens of this species 

 from 129 samples (Table 5). 



Our samples are similarly distributed in that they range 

 from the Scotian Shelf off Nova Scotia south to slightly north 

 of Miami, Fla., occupying nearly the whole of the east coast 

 continental shelf (Fig. 57; Theroux and Wigley footnote 4, 

 table 97). 



The main distribution is Boreal, Virginian, and Caribbean 

 in the northwest Atlantic (Coomans 1962). Gosner (1971) 

 listed it as occupying the Boreal and Virginian provinces, 

 while Dance (1974) assigned it to the Boreal and Transatlantic 

 provinces in eastern North America. 



The depth range for this species is from low water at + 1 to 

 62 m (Abbott 1974; Porter 1974). 



Our samples range from to 80 m depth with a mean of 38 

 m. The 0-24 m depth range grouping contains 33% of the 

 samples and 22% of the specimens; the 25-49 m grouping 

 contains 35% of the samples and 46% of the specimens, and 

 the 50-99 m grouping contains 33% of the samples and 32% of 

 the specimens (Table 290). 



This species occupies sand and sandy mud bottoms (Morris 

 1951; Abbott 1968). 



Among the various types of sediments in which we found 

 this species the majority occupied sand substrates which 

 yielded 78% of the samples and 91% of the specimens. Signifi- 

 cantly smaller amounts occurred in sand-gravel, sand-shell, 

 silty sand, silt, and clay substrates (Table 291). There are 14 



'"Abbott (1974) has "Conrad, 1831" for this species, it should be Conrad 

 1830. see under References. 



samples containing 52 specimens which are unclassified with 

 regard to sediment type. 



Lyonsia sp. Figure 56. 



The NEFC collection contains five specimens from six 

 samples classified to the generic level Lyonsia (Table 5). 



The five samples of this taxon are from inshore areas and 

 the outer continental shelf of the Middle Atlantic Bight region 

 between Cape Cod, Mass., and the offing of Chesapeake Bay 

 (Fig. 56; Theroux and Wigley footnote 4, table 98). 



Our samples are from waters which range from 8 to 63 m in 

 depth with a mean of 39 m. Forty percent of the samples occur 

 in the 0-24 and 50-99 m depth range groupings which contain 

 33 and 50% of the specimens, respectively; the 25-49 m group- 

 ing contains 20% of the samples and 17% of the specimens 

 (Table 292). 



Members of this taxon occurred in three sediment types, 

 the majority of samples (60%), as well as specimens (67%), 

 were obtained from sand substrates; sand-gravel, and silty 

 sand each contained 20% of the samples and 17% of the 

 specimens (Table 293). 



Family PERIPLOMATIDAE 

 Genus Periploma Schumacher 1816 



Periploma affine Verrill and Bush 1898. Figure 85. 



According to Johnson (1934) and Abbott (1974), this spe- 

 cies occurs only off Martha's Vineyard, Mass. 



The NEFC collection contains 21 specimens from 2 sam- 

 ples of this rather rare bivalve species (Table 5). 



The two samples in the NEFC Specimen Reference Collec- 

 tion are from off the tip of Cape Cod, Mass., in Cape Cod Bay 

 (Fig. 85; Theroux and Wigley footnote 4, table 147). 



According to the previously cited authors the depth range 

 of this species is from 183 to 211 m. 



Our samples are from 46 and 49 m of water, placing them in 

 the 25-49 m depth range grouping. 



This species was found in two substrate types, till and clay. 

 each containing 50% of the samples; however, the tilloid 

 substrate contained 95% of the specimens while the sample in 

 clay contained 5% of the specimens. 



Periploma fragile (Totten 1835). Fragile spoon clam. Figure 85. 



The distribution of the fragile spoon clam is from New- 

 foundland and Labrador to Cape Cod, Mass., with Arctic 

 outposts at the Parry Islands (Johnson 1934; Morris 1951, 

 1973; La Rocque 1953; Ockelmann 1958; Abbott 1974). 



Periploma fragile is represented in the NEFC collection by 

 101 specimens obtained from 27 samples (Table 5). 



The NEFC samples are from three separate areas; two 

 samples occur in the Gulf of Maine off Portland. Maine, 

 another group of samples is on the southern New England 

 shelf and slope area south of Nantucket Shoals, and two more 

 samples occur on the continental shelf off Atlantic City. N.J. 

 (Fig. 85; Theroux and Wigley footnote 4, table 148). 



Coomans (1962) placed this species in the Boreal and Virgi- 

 nian provinces. 



The fragile spoon clam is a moderately shallow water in- 

 habitant whose depth distribution ranges between 7 and 73 m 

 (Abbott 1974). 



53 



