162 
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. 
Station 
Date 
Com- 
pressa 
Bispi- 
nosa 
Station 
Date 
Com- 
pressa 
Bispi- 
nosa 
10047. 
Nov. 20, 1912 
20 
12 
10051 
Jan. 30,1913 
4 
0 
10048. 
Deo. 4, 1912 
15 
25 
10052... 
do__ 
25 
3 
10049 
Dec. 23, 1912 
15 
12 
10053 . 
Feb. 13, 1913 
30 
10050 
Jan. 16,1913 
30 
2 
10054 
Mar. 4,1913 
20 
0 
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. 
