which contained 92% of the samples and 93% of the speci- 

 mens. The only other sediment type in which specimens were 

 found was sand-gravel which contained 8% of the samples 

 and 7% of the specimens (Table 307). There is one sample 

 containing one specimen which is unclassified with regard to 

 sediment type. 



Family POROMYIDAE 

 Genus Poromya Forbes 1844 



Poromya sp. Figure 91. 



The NEFC collection contains six specimens from six sam- 

 ples which are classified as Poromya sp. (Table 5). 



The samples containing specimens of Poromya are distri- 

 buted on the edge of the continental shelf with two samples 

 occurring between Delaware and Chesapeake Bays ; two sam- 

 ples, one north and one south of Cape Hatteras, N.C., and 

 two between Charleston, N.C., and Jacksonville, Fla. (Fig. 

 91; Theroux and Wigley footnote 4, table 159). 



Our samples are from depths which range between 17 and 

 400 m with a mean of 131 m. The 0-24 and the 200-499 m 

 groupings each contain 17% of both samples and specimens, 

 while the 25-49 and 100-199 m groupings each contain 33% of 

 both samples and specimens (Table 308). 



Samples containing Poromya were obtained from three 

 sediment types: sand-shell, sand, and silty sand. Sand subs- 

 trates contained 50% of both samples and specimens, while 

 sand-shell contained 17% for each and silty sand 33% for each 

 (Table 309). 



Family CUSPIDARIIDAE 



There are 1 1 specimens from 9 samples in the NEFC collec- 

 tion classified as Cuspidariidae (Table 5). 



Samples containing members of this taxon are from the 

 continental shelf and upper slope in the southern regions of 

 the study area extending from south of Cape Fear, N.C., to 

 Key West, Fla. (Fig. 37; Theroux and Wigley footnote 4, table 

 60). 



The depth range of our samples is 30 to 257 m with a mean of 

 156 m. The majority of samples and specimens are in the 

 200-499 m depth range grouping accounting for 45%' of both 

 samples and specimens. Two of the depth range groupings, 

 the 50-99 m and the 100-199 m, each account for 22% of the 

 samples but 18 and 23% of the specimens, respectively. The 

 shallowest depth range grouping, 25-49 m. contains 11% of 

 the samples and 9% of the specimens (Table 310). 



This taxon was found in three sediment types, sand-shell, 

 sand, and silty sand. Sand substrates predominate in both 

 sample and specimen strength containing 56% of the former 

 and 55% of the latter. One-third of the samples occurred in 

 silty sand which contained 36% of the specimens; whereas, 

 sand-shell substrates contained 1 1% of the samples and 9% of 

 the specimens (Table 311). 



Genus Cardiomya Adams 1864 



Cardiomya perrostrata (Dall 1881). West Indian dipper shell. 

 Figure 22. 



This species occurs from south of Martha's Vineyard, 



Mass., to the West Indies and Brazil (Johnson 1934; Morris 

 1973; Abbott 1974). 



There are 24 specimens from 13 samples of this species in 

 the NEFC collection (Table 5). 



Our samples are distributed along the outer continental 

 shelf and slope in the Middle Atlantic Bight Region between 

 Cape Cod, Mass., and Cape Hatteras, N.C. (Fig. 22; Theroux 

 and Wigley footnote 4, table 35). 



The West Indian dipper shell occupies the Virginian pro- 

 vince (Gosner 1971). 



The depth range of this species is 106 to 761 m (Johnson 

 1934). 



Our samples are from water depths ranging from 141 to 500 

 m with a mean of 212 m. The majority of both samples (77%) 

 and specimens (88%) are in the 100-199 m depth range 

 grouping; diminishing amounts of each occur in the 200-499 m 

 and 500-999 m groupings (Table 312). 



Members of this species were found in sand, silty sand, silt, 

 and clay substrates. There is a general tendency of decreasing 

 abundance of both samples and specimens with decreasing 

 sediment particle size (Table 313). 



Genus Cuspidaria Nardo (1840) 



Cuspidaria glacialis (G. O. Sars 1878). Northern dipper shell. 

 Figure 34. 



The northern dipper shell is widely distributed throughout 

 the Northern Hemisphere, occurring in both the North Atlan- 

 tic and North Pacific Oceans. Ockelmann (1958) and Clarke 

 (1962) have extensive lists of its Arctic and subarctic distribu- 

 tion, claiming that it is panarctic but probably abyssal only in 

 the North Atlantic. Other authorities report its distribution to 

 be from Canadian Arctic seas south to Florida in the Atlantic 

 and from Alaska to San Diego, Calif., in the Pacific (Johnson 

 1934;Morris 1951, 1973;LaRocque 1953; Abbott 1968, 1974). 



The NEFC collection contains 184 specimens of this com- 

 mon species from 49 samples (Table 5). 



Samples in our collection are primarily in the Gulf of Maine 

 region; however, a few isolated samples occur in the Middle 

 Atlantic Bight off Long Island, N.Y., a few off Atlantic City, 

 N.J., and two occur farther south on the continental slope 

 east of Norfolk, Va. (Fig. 34; Theroux and Wigley footnote 4, 

 table 54). 



The zoogeographic provinces occupied by this species are 

 the Boreal and Virginian (Gosner 1971). 



The reported depth range for this species is from 15 to 2,685 

 m (Johnson 1934; Clarke 1962; Abbott 1968). 



The NEFC samples are from depths which range from 75 to 

 3,820 m with a mean of 281 m. The majority of our samples 

 (55%) and specimens (60%) are in the 100-199 m depth range 

 grouping; the 50-99 m and the 200-499 m groupings each 

 contain 18% of the samples but 23 and 13% of the specimens, 

 respectively. Six percent of the samples and 4% of the speci- 

 mens are in the 500-999 m grouping and 2 and 0.5%, respec- 

 tively, in the 2,000-3,999 m grouping (Table 314). 



This species is an inhabitant of sand substrates (Abbott 

 1968). 



Our samples were found in gravel, till, sand, silty sand, silt, 

 and clay substrates. Table 315 lists the amounts of samples 

 and specimens that were found in each sediment type. One 

 sample containing three specimens is unclassified with regard 

 to sediment type. 



56 



