groupings shows a diminution in abundance of both samples 

 and specimens with increasing water depth range. Greatest 

 amounts are in the 0-24 depth range grouping which contains 

 43% of the samples and 38% of the specimens; the 25-49 m 

 depth range grouping contains 40% of the samples and 34% of 

 the specimens while the 50-99 m grouping contains 14 and 

 21%, respectively; 2% of the samples occur in the 200-499 and 

 1,000-1,999 m depth range groupings, each of which con- 

 tained 1 and 6%, respectively, of the specimens (Table 162). 

 Members of the genus Diplodonta occurred in sand-shell, 

 sand, silty sand, and silt sediments. Sand-shell sediments 

 contained 19% of the samples and 18% of the specimens, 

 while sand substrates yielded 74% of the samples and 73% of 

 the specimens; amounts diminished as particle size dimin- 

 ished. Silty sand contained 5% of the samples and 3% of the 

 specimens while silt contained 2% of the samples and 6% of 

 the specimens (Table 163). 



Family CHAMIDAE 

 Genus Arcinella Oken 1815 



Arcinella cornuta Conrad 1866. Florida spiny jewel box. Figure 



7. 



This species occurs from North Carolina to Florida and the 

 West Indies in the Atlantic and from the west coast of Florida 

 to Texas in the Gulf of Mexico (Abbott 1968, 1974; Morris 

 1973; Emerson et al. 1976). 



Our collection contains three specimens from three sam- 

 ples of this common bivalve (Table 5), the samples are from 

 the continental shelf between Charleston, S.C., and Jackson- 

 ville, Fla. (Fig. 7; Theroux and Wigley footnote 4, table 12). 



Abbott (1968, 1974) reported a depth range of 3.7 to 73 m for 

 this species. 



Our samples range in depth from 19 to 35 m with a mean of 

 29 m. Thirty-three percent of samples and specimens are in 

 the 0-24 m depth range grouping, the remaining samples and 

 specimens (67% for each) are in the 25-49 m depth range 

 grouping (Table 164). 



The only mention of sediment relation in reports we have 

 seen is a reference to this species being found on old shells 

 (Abbott 1968). Sixty-seven percent of our samples and speci- 

 mens occurred in sand, and 33% of each were from a sand 

 shell substratum (Table 165). 



Family CARDIIDAE 

 Genus Chama Linne 1758 



Chama sp. Figure 24. 



The NEFC collection contains one sample containing one 

 specimen of material which was identified to the generic level 

 of Chama sp. (Table 5). 



The sample containing the specimen is from off Miami, Fla. 

 (Fig. 24; Theroux and Wigley footnote 4, table 37). 



Our sample of Chama is from a water depth of 42 m in a 

 substrate of sand. 



Family LASAEIDAE 

 Genus Aligena Lea 1843 



Aligena elevata (Stimpson 1851). Eastern aligena. Figure 3. 



The eastern aligena is distributed from Massachusetts to 

 North Carolina (Johnson 1934; Abbott 1974; Emerson et al. 

 1976). 



There are two samples containing three specimens of this 

 species in the NEFC collection (Table 5). Abbott (1974) and 

 Emerson et al. (1976) considered it a common species. 



Our samples are from Nantucket Sound and just off the 

 outer shore of Long Island, N.Y. (Fig. 3; Theroux and Wigley 

 footnote 4, table 5). 



Abbott (1974) reported that the depth range of A. elevata is 

 from the shoreline to 18 m, while Porter (1974) reported it 

 from 0.3 to 11 m. 



Our two samples are from 18 and 31 m depths with a mean 

 of 25 m. Two specimens occurred in the shallower depth and 

 one at the deeper site. 



Both of our samples for this species were in a sand sub- 

 stratum. 



Family LEPTON1DAE 

 Genus Montacuta Turton 1822 



Montacuta sp. Figure 63. 



The NEFC collection contains one specimen from one 

 sample of this genus (Table 5). 



The sample in the NEFC collection is from inshore waters 

 at the elbow of Cape Cod. Mass. (Fig. 63: Theroux and Wigley 

 footnote 4, table 109). The depth from which this sample was 

 taken is 18 m which places it in the 0-24 m depth range 

 grouping. The sediment type was sand. 



Genus My sella Angas 1877 

 Mysella sp. Figure 69. 



The NEFC Specimen Reference Collection contains two 

 members of this genus from one sample (Table 5). 



Our sample is from the upper portion of the continental 

 slope off the midsection of the Florida Peninsula (Fig. 69; 

 Theroux and Wigley footnote 4. table 1 18). The sample was in 

 a water depth of 400 m placing it in the 200-499 m depth range 

 grouping. Substrate type at the sampling site was silt. 



Family TURTONHDAE 

 Genus Turtonia Alder 1848 



Turtonia sp. Figure 115. 



Our collection contains one sample which yielded one 

 specimen of the genus Turtonia (Table 5). 



Our sample is from the northern edge of Browns Bank ( Fig. 

 1 15; Theroux and Wigley footnote 4. table 206). The sample is 

 from a water depth of 1 19 m placing it in the 100-199 m depth 

 range grouping, and is from a gravel substratum. 



30 



