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BULLETIN OF THE BUREAU OF FISHERIES 



on November 10 (station 10405), but farther out on the continental shelf on this 

 line bispinosa predominated in the rich catches of these amphipods (stations 10406 

 and 10407). 



In Massachusetts Bay, which may be taken as fairly representative of the western 

 coastal waters of the gulf, E. bispinosa attains its greatest numerical strength, com- 

 pared to E. compressa, during late autumn or early winter, dwindling rapidly there- 

 after, as appears from the following table of the relative abundance of the two 

 species in samples of the catches made off Gloucester during the winter of 1912-1913. 



Although it is not yet possible to outline the relationship of the two species 

 more in detail, it is safe to say that E. compressa is a permanent and characteristic 

 inhabitant of all parts of the Gulf of Maine except the immediate coastal zone, 

 occurring there wherever the genus is known at all, and at all seasons. E. bispinosa 

 is to be found over the outer parts of the continental shelf throughout the year, 

 but it is only a seasonal visitor to the inner parts of the gulf, spreading first into its 

 eastern half in summer. By autumn and early winter it may rival compressa locally 

 right up to the western and northern shores of the gulf, but in the western coastal 

 zone it is usually outnumbered by the latter even at that season, and either perishes 

 or withdraws seaward once more with the advance of winter. 



Thus, E. bispinosa is decidedly more oceanic than E. compressa, as it occurs 

 in the inner parts of the gulf, which corresponds to the fact that it usually equals 

 or predominates over the latter in the coast waters south of Nova Scotia, over the 

 whole southern part of Georges Bank, and in the shallow waters south of Marthas 

 Vineyard and Nantucket. It is also more oceanic than compressa on the European 

 side of the Atlantic, seldom appearing within the North Sea, but regularly present 

 off the west coast of Ireland (Tesch, 1911; Tattersall, 1911), well out from the west 

 coast of France, at least in autumn (Le Danois, 1921), and in the colder waters 

 of the Norwegian and Arctic Seas. But with the two species in roughly equal 

 numbers in the rather scant catches outside the continental edge, or with compressa 

 and not bispinosa predominating there (sometimes, in fact, the only member of the 

 pair represented, as at station 20064 on March 11, 1920), the relative status of the 

 two species off the North American littoral can not be established without further 

 study. 



As a general rule, when bispinosa outnumbers compressa its preponderance is 

 greatest in the deep hauls, whether in the gulf, over the banks, or west and south 

 of Cape Cod. 



The adult Euthemisto are not characteristic of any precise depth level in the 

 water, as is the large copepod Euchseta norvegica, for example (p. 29), but occur 

 at all depths from the surface down to the deepest strata of the Gulf of Maine. 



