Family CARDITIDAE 



Genus Cyclocardia Conrad 1867 



Cyclocardia borealis (Conrad 1831). Northern cardita. Figure 

 38. 



The northern cardita is reported from both the North Atlan- 

 tic and North Pacific Oceans, but is more common in the 

 North Atlantic extending from the Arctic Ocean to Cape 

 Hatteras, N.C., while in the Pacific it ranges from the Arctic 

 Ocean to Oregon; it is also found in subarctic regions, ranging 

 from the Parry Islands to and including Labrador (Dall 1902b; 

 Johnson 1934: Morris 1951, and 1973; LaRocque 1953; Ockel- 

 mann 1958; Abbott 1974; Emerson et al. 1976). 



Cyclocardia borealis is a very common bivalve species in 

 the northwest Atlantic. This commonness is reflected in the 

 NEFC collection where there are 475 samples, representing 

 4.5% of all samples, containing 8,842, or 8.1% of all speci- 

 mens (Table 5). 



The NEFC samples are from continental shelf and slope 

 waters in the northern reaches of the study area including the 

 Scotian Shelf on the east and west coasts of Nova Scotia, 

 throughout the Gulf of Maine-Georges Bank complex, on the 

 Southern New England shelf and slope to north and east of 

 Cape Hatteras. N.C. (Fig. 38; Theroux and Wigley footnote 4, 

 table 61). There are two apparently disparate samples, one 

 south of Charleston, S.C.. on the continental shelf and the 

 other in the inner Florida Keys; these will be investigated 

 further to determine whether they are range extensions or 

 not. 



The zoogeographic range is Boreal and Virginian (Coomans 

 1962: Gosner 1971); whereas, Dance (1974) listed it as occur- 

 ring in the Boreal and Transatlantic provinces. 



The bathymetric range is 1 .8 to 796 m (Abbott 1968; Porter 



1974). 



Our samples are from depths between 15 and 293 m with a 

 mean of 9 1 m. The 50-99 m depth range grouping contains 56% 

 of the samples and 63% of the specimens; next greatest 

 amounts are in the 100-199 m grouping which contains 24 and 

 25% of samples and specimens, respectively. The 25-49 m 

 grouping contains 13% of the samples and 11% of the spe- 

 cimens; the 0-24 m grouping 3 and 0.4%, respectively, while 

 the 200-499 m grouping contains 4.4 and 1% of samples and 

 specimens, respectively (Table 166). Two samples containing 

 three specimens have no associated depth information. 



Specimens of the northern cardita were found in all of the 

 sediment types considered in this report. The greatest number 

 of samples (36%) were found in sand, but the largest number 

 of specimens (38%) were obtained in till. Sand, silty sand, and 

 clay substrates contained between 15 and 22% of the speci- 

 mens in each type and silty sand and clay contained 1 3 to 14% 

 of the specimens (Table 167). Forty-five samples containing 

 148 specimens are unclassified with regard to sediment type. 



Cyclocardia novangliae (Morse 1869). Figure 39. 



For many years Cyclocardia novangliae has been consid- 



ered to be a variety of Cyclocardia borealis. It has recently 

 achieved the status of a valid species (J. J. Kosmark 5 ). 



The range of this species extends from Newfoundland to 

 Cape Cod, Mass. (Johnson 1934; La Rocque 1953). Abbott 

 (1974) reported it to be distributed from Nova Scotia to New 

 York. 



There are 89 specimens from 26 samples of this species in 

 the NEFC collection (Table 5). 



The samples in our collection are from the Nova Scotian 

 banks and shelf, the Gulf of Maine continental shelf off the 

 coast of Maine, and the Northeast Peak of Georges Bank as 

 well as Great South Channel southeast of Cape Cod (Fig. 39: 

 Theroux and Wigley footnote 4, table 62). 



The range in depth from which our specimens were 

 obtained is 46 to 249 m with a mean of 95 m. The 50-99 m depth 

 range grouping contains the largest amount of both samples 

 (65%) and specimens (90%). Twenty-three percent of the 

 samples and 7% of the specimens are in the 100-199 m depth 

 range grouping. 8%- of the samples and 2% of the specimens 

 occur in the 25-49 m grouping, and 4 and 1%, respectively, in 

 the 200-499 m grouping (Table 168). 



Sand-gravel was the predominant substrate type containing 

 44% of the samples and 43% of the specimens, while gravel, 

 although containing 20% of the samples, contained only 7% of 

 the specimens; till substrates yielded 12%' of the samples and 

 27% of the specimens; shell and sand each contained 8% of 

 the samples but 18 and 2% of the specimens, respectively: 

 both clay and sand-shell each contained 4% of the samples 

 and 1% of the specimens (Table 169). There is one sample 

 containing one specimen which is unclassified with regard to 

 sediment type. 



Cyclocardia sp. Figure 39. 



There are 22 specimens from 16 samples in the NEFC 

 collection which are identified as Cyclocardia sp. (Table 5). 



The NEFC samples of this taxon are located on the con- 

 tinental shelf from Cape Hatteras southward to just north of 

 Miami, Fla. (Fig. 39; Theroux and Wiglev footnote 4. table 

 63). 



Water depths at which our samples of Cyclocardia were 

 obtained range between 8 and 80 m with a mean of 30 m. Three 

 depth range groupings are involved with this distribution. 

 50% of the samples and 59%- of the specimens are in the 0-24 m 

 depth range grouping, 38% of the samples and 32% of the 

 specimens are in the 25-49 m grouping, and 13 and 9% of 

 samples and specimens, respectively, are in the 50-99 m 

 grouping (Table 170). 



Fifty percent of the samples and specimens occurred in 

 sand-shell substrates while sand sediments contained 31 and 

 32%, respectively. Each of the following sediment types con- 

 tained 6% of the samples: gravel, shell, and silty sand: gravel 

 and shell substrates contained 5% of the specimens, while 9% 

 of the specimens were obtained from silty sand substrates 

 (Table 171). 



'J. J. Kosmark. graduate student. Graduate School of Oceanography. Uni- 

 versity of Rhode Island. Kingston. RI 02881. pers. Commun. May 1978. 



31 



