occurs in both the North Atlantic and North Pacific Oceans. 

 The Atlantic distribution extends from Greenland to North 

 Carolina in the region of Cape Hatteras. It is also reported 

 from the Gulf of Mexico and the Caribbean. In the Pacific it is 

 distributed from the low Arctic regions to California and 

 Korea. It also occurs off the northern Eurasian continent, in 

 western Europe, Norway, and is considerably distributed 

 throughout the Arctic, south to the British Isles (Johnson 

 1934;LaRocque 1953; Ockelmann 1958; Clarke 1962;Tebble 

 1966; Morris 1973; Abbott 1974). 



Crenella decussata is represented in the NEFC collection 

 by 443 specimens from 83 samples (Table 5). 



Our samples are from the fishing banks east of Nova Scotia, 

 the Scotian Shelf, the Gulf of Maine basin, on the periphery of 

 Georges Bank, and on the outer continental shelf in the Mid- 

 dle Atlantic Bight region south to Cape Hatteras. N.C.; one 

 sample occurs south of Cape Fear on the mid-continental 

 shelf (Fig. 31; Theroux and Wigley footnote 4, table 50). 



The zoogeographic provinces occupied by this species are 

 the Arctic, the Boreal, the Virginian, and Celtic in Europe 

 (Coomans 1962), while Ockelmann (1958) listed it as low 

 Arctic-boreal and circumpolar. 



This small bivalve has a considerable bathymetric range 

 occurring from just offshore out to considerable depths, a 

 depth range extending from 4 to 3,203 m (Clarke 1962); 

 however, Ockelmann (1958) reported that in northern seas 

 this species is mainly littoral. 



The depth range of our samples is from 23 to 201 m with a 

 mean of 83 m. The distribution of our samples with regard to 

 depth range groupings is as follows: 62% of the samples and 

 68% of the specimens are in the 50-99 m depth range grouping: 

 21% of the samples and 13% of the specimens are in the 

 100-199 m depth grouping, while 12% of the samples but 18% 

 of the specimens are in the 25-49 m grouping; the 0-24 m 

 grouping contains 4% of the samples and only 1% of the 

 specimens, while the 200-499 m grouping contains 2% of the 

 samples and 0.5% of the specimens (Table 86). 



This species occurs in sand and clay and on sand or gravel 

 bottoms (Tebble 1966); Morris (1973) considered it to inhabit 

 mud bottoms. 



Our samples occurred in all but one of the nine sediment 

 types we are using for purposes of this report, none were 

 found in sand-shell. Sand, silty-sand, and clay substrates 

 were preferred, 35% of the samples and 25% of the specimens 

 occurred in sand: silty sand contained 30% of the samples and 

 56% of the specimens, while clay substrates contained 17% of 

 the samples and 9% of the specimens. Significantly smaller 

 amounts occurred in the remaining sediment types, gravel, 

 sand-gravel, till, shell, and silt (Table 87). Two samples con- 

 taining four specimens are unclassified with regard to sedi- 

 ment type. 



Crenella glandula (Totten 1834). Glandula crenella. Figure 32. 



This very common mussel is distributed from Labrador to 

 North Carolina (Johnson 1934; La Rocque 1953; Ockelmann 

 1958; Morris 1973; Abbott 1974). 



This small mussel is represented in the NEFC collection by 

 229 samples (2.2% of samples) containing 1.135 specimens 

 (1.7% of specimens) (Table 5). 



Our samples are widely distributed on the continental shelf 

 and upper slope; they range from both sides of Nova Scotia, 



throughout the Gulf of Maine, onto Georges Bank, and the 

 Southern New England shelf and slope, into the Middle 

 Atlantic Bight region, south to the mouth of Chesapeake Bay 

 (Fig. 32; Theroux and Wigley footnote 4, table 51). 



This species occupies the Boreal and Virginian zoogeo- 

 graphic provinces (Coomans 1962). 



The bathymetric range of this species is from 6 to 110 m 

 (Johnson 1934). 



The depth range of our samples is from to 406 m with a 

 mean of 99 m. Distribution of samples and specimens with 

 regard to depth range groupings is 4% of the samples and 6% 

 of the specimens are in the 0-24 m grouping, while 9% of the 

 samples but 46% of the specimens are in the 25-49 m depth 

 range grouping; the largest number of samples (55%) are in the 

 50-99 m depth range grouping, but it contains only 31% of the 

 specimens; 30% of the samples and 16% of the specimens are 

 in the 100- 199 m grouping and 4% of the samples and 1% of the 

 specimens are in the 200-499 m grouping (Table 88). 



Crenella glandula occurred in all of our sediment types. 

 There appears to be a preference for till, sand, silty-sand, and 

 clay sediments both in terms of numbers of samples found in 

 these sediment types as well as the number of specimens; 

 significantly smaller amounts are found in gravel, sand- 

 gravel, shell, sand-shell, and silt substrate types. Table 89 

 lists the pertinent data for this species in relation to bottom 

 sediments. Twenty-four samples containing 139 specimens 

 are unclassified with regard to sediment type. 



Crenella sp. Figure 33. 



The NEFC collection contains 35 samples with 69 speci- 

 mens identified to the generic level of Crenella sp. (Table 5). 



Samples in our collection containing members of this genus 

 are from the Gulf of Maine, Georges Bank, the Middle Atlan- 

 tic Bight, off the coast of South Carolina, and the mid-section 

 of Florida off Jacksonville (Fig. 33; Theroux and Wigley 

 footnote 4, table 52). 



Members of this genus are found in the Arctic, Boreal, and 

 Virginian provinces in the northwest Atlantic, and in the 

 Celtic province in Europe (Coomans 1962). 



The depth range of our samples is 15 to 2,412 m with a mean 

 of 209 m. The majority of samples are in the 100-199 m depth 

 range grouping which contains 37% of the samples and 57% of 

 the specimens. The 50-99 m grouping contains 29% of the 

 samples and 19% of the specimens; the 0-24 and 25-49 m 

 groupings each contain 14% of the samples but 7 and 13% of 

 the specimens, respectively; 3% of the sarnies are in the two 

 deepest range groupings, 1,000-1,999 and 2,000-3,999 m 

 which account for 3 and 1% of the specimens, respectively 

 (Table 90). 



Samples containing Crenella sp. occurred in all but one 

 sediment type, till. Sand yielded the largest amount of sam- 

 ples (34%) followed by silty sand (22%) and gravel (13%); the 

 other sediment types had amounts ranging between 3 and 9%. 

 Sand-gravel yielded the greatest amount of specimens (29%) 

 closely followed by sand (27%); much smaller amounts (3 to 

 11%) occurred in other sediment types (Table 91). There are 

 three samples containing six specimens which are unclassi- 

 fied with regard to sediment type. 



16 



