Morris (1973), Abbott (1974), and Emerson et al. (1976) 

 stated that this moderately common species, which is plenti- 

 ful at Eastport and other coastal areas in Maine, ranges in 

 depth from the low tide line to approximately 110 m. 



The NEFC samples are from water depths of 38 and 42 m 

 which places them in the 25-49 m depth range grouping. 



Chamberlin and Stearns (1963) reported that Stimpson's 

 surf clam is normally found in medium sediments of sand, 

 gravel, and mixtures of sand gravel. Unfortunately, there was 

 no sediment information contained in the sampling data of the 

 samples from which we obtained our specimens. 



Spisula solidissima (Dillwvn 1817). Atlantic surf clam. Figure 

 101. 



Spisula solidissima is one of the most economically impor- 

 tant shellfish resources of the U.S. east coast. Landings in 

 1977 were 51.0 million pounds of meats valued at $26.4 mil- 

 lion, in 1978 landings decreased to 39.2 million pounds of meat 

 with a value of $20.9 million (Pileggi and Thompson 1979). As 

 such, it is, and has been, the subject of intensive studies by 

 various elements of the old Bureau of Commercial Fisheries 

 and presently the NEFC of the NMFS. As with other com- 

 mercially important bivalve species, the NEFC possesses a 

 broad data base on this species: however, the data herein 

 presented are based solely on the collections which physically 

 reside in the Specimen Reference Collection at the NEFC. 



This species is known by a variety of common names in 

 addition to that which appears above: surf clam: hen clam: sea 

 clam: bar clam: skimmer; dipper clam; beach clam: and giant 

 clam, and is extremely important in some areas, especially in 

 the inshore and near offshore waters of coastal New Jersey 

 between Sandy Hook and Cape May. 



The Atlantic surf clam is normally found in some outlying 

 areas of the Arctic but principally from the Gulf of St. Law- 

 rence to Cape Hatteras. N.C. (Johnson 1934: Morris 1951. 

 1973: La Rocque 1953; Ockelman 1958; Abbott 1968, 1974; 

 Yancey and Welch 1968: Emerson et al. 1976). 



The NEFC collection has on hand 764 specimens from 166 

 samples (Table 5). 



The NEFC samples are from the continental shelf ranging 

 from the Nova Scotian shelf and Browns Bank, the inshore 

 regions of the Gulf of Maine and the Cape Cod region out onto 

 Georges Bank and south to approximately Jacksonville, Fla. 

 (Fig. 101; Theroux and Wigley footnote 4. table 180). 



This species inhabits the Boreal. Virginian, and Carolinian 

 provinces in the northwest Atlantic: the genus and family are 

 Celtic in Europe which harbors another species, Spisula soli- 

 da (Coomans 1962): Gosner(1971) placed it in the Boreal and 

 Virginian provinces, while Dance ( 1974) stated it occupies the 

 Boreal and Transatlantic zoogeographic provinces. 



Although the Atlantic surf clam primarily inhabits inshore, 

 shallow waters, it does range out to 146 m depth (Abbott 1968. 

 1974; Yancey and Welch 1968). 



The depth range of our samples is to 1 10 m with a mean of 

 33 m. In terms of depth range groupings, the majority of both 

 samples and specimens are in the shallowest. 0-24 m group- 

 ing, which contains 42% of the samples and 67% of the spe- 

 cimens; the 25-49 m grouping contains 40% of the samples and 

 27% of the specimens: the 50-99 m grouping, 17% of the 

 samples and 6% of the specimens: only 2% of the samples and 

 0.4% of the specimens are in the 100-199 m grouping (Table 



204). There are 2 samples containing 21 specimens which do 

 not contain depth information in their sampling data. 



Morris (1951) and Yancey and Welch (1968) reported that 

 this species is normally found in sand and gravel substrates. 



Our samples were found in nearly all substrate types con- 

 sidered in this report, the only exceptions were till and clay. 

 The major sediment type was sand which contained 69% of 

 the samples and 82% of the specimens; next greatest abun- 

 dance of both samples and specimens occurred in sand-shell 

 substrates which contained 12% of the samples and 10% of the 

 specimens; gravel, sand-gravel, shell, silty sand, and silt sub- 

 strates, although containing samples which yielded speci- 

 mens of Spisula solidissima, contained significantly smaller 

 amounts of both samples and specimens (Table 205). There 

 are 40 samples containing 96 specimens which are unclassi- 

 fied with regard to sediment type. 



Family MESODESMATIDAE 

 Genus Ervilia Turton 1822 



Ervilia concentrica (Holmes 1860). Concentric ervilia. Figure 

 44. 



The concentric ervilia is a southern species occurring from 

 North Carolina to both sides of Florida and to Brazil, it is also 

 found at Bermuda (Johnson 1934; Abbott 1974). 



Ervilia concentrica is a common warm water species of 

 which there are 192 specimens from 1 12 samples in our collec- 

 tion (Table 5). 



Our samples range from just north of Cape Hatteras, N.C, 

 to the southern two-thirds of Florida (Fig. 44: Theroux and 

 Wigley footnote 4, table 72). 



Abbott (1974) and Porter (1974) reported a bathymetric 

 range for this species which extends from 0.3 to 92 m in depth. 



Our samples are from water depths which range from 6 to 50 

 m with a mean of 24 m. Three depth range groupings are 

 occupied with diminishing abundance as depth range in- 

 creases. The 0-24 m depth range grouping contains 54% of the 

 samples and 55% of the specimens; the 25-49 m grouping 

 contains 45% of the samples and 44% of the specimens, while 

 the 50-99 m grouping contains 2% of the samples and < 1% of 

 the specimens (Table 206). 



Sand substrates were decidedly preferred over other types 

 of sediments, accounting for 63% of the samples and 61% of 

 the specimens. Next preferred sediment type, sand-shell, 

 contained 28% of the samples and 30% of the specimens. 

 Gravel, sand-gravel, silty sand, and silt substrates contained 

 between 1 and 4% of the samples, and 0.3 to 3% of the 

 specimens (Table 207). 



Genus Mesodesma Deshayes 1831 



Mesodesma arctatum (Conrad 1830). Arctic wedge clam. Figure 

 61. 



This species ranges from Greenland to Chesapeake Bay 

 and Virginia (Johnson 1934; Morris 1951, 1973; La Rocque 

 1953; Ockelmann 1958; Abbott 1968, 1974; Emerson et al. 

 1976). 



There are 52 specimens from 2 samples of Arctic wedge 

 clams in the NEFC collection (Table 5). 



38 



