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BULLETIN OF THE BUREAU OF FISHERIES 
(1913) points out, but before it can be used in this way for American waters a far 
clearer insight must be gained into its hydrographic and geographic relationships. 
In fact, it is still an open question whether Th. longissima is oceanic or neritic in the 
western Atlantic, or as indifferent to the proximity of coasts or shallows as it is on 
the European side. 
Thalassiothrix nitschioides, although one of the most characteristically neritic 
of all pelagic diatoms, has occurred far more often in our tow nettings than has its 
relative, Th. longissima. Fritz (1921) found Th. nitschioides at St. Andrews through- 
out the year except between October 15 and December 13, and the numbers counted 
were usually so small that its absence from the hauls made during that period is 
perhaps not significant. Probably it occurs irregularly the year round in similar 
situations all along the coast line of the gulf, and its presence or absence and its rela- 
tive abundance out at sea may depend more on the currents sweeping it out from 
these sources of supply around the coast line than on local flowerings. 
It seems that few drift out to sea during the winter, for it was detected at only 
one station — off the mouth of the Merrimac River (station 10492) — during the mid- 
winter cruise of the Halcyon in 1920 and 1921, and not at all in our tows off Gloucester 
from November, 1912, to February, 1913. But we had it off the western part of 
Georges Bank on February 22, 1920 (station 20045), and during that March it was 
found at four stations in the coastal belt between Cape Cod and the Bay of Fundy; 
also in the Eastern Channel, on the southeastern slope of Georges Bank, and at two 
stations off Shelburne, Nova Scotia (stations 20056, 20058, 20059, 20064, 20066, 
20068, 20071, 20075, 20076, 20084, and 20088; fig. 127). Th. nitschioides attains 
its widest distribution in the gulf in April, during which month in 1920 it not only 
occurred more regularly in the coastal belt than in March (in fact, at almost every 
inshore station where diatoms of any sort were plentiful), and off Nova Scotia out to 
the southeastern slope of Georges Bank, but likewise at four localities in the central 
basin of the gulf (stations 20089 to 20093; 20095 to 20098; 20100, 20102 to 20107, 
20109, 20114, and 20117). 
Our records suggest that Th. nitschioides practically disappears again from the 
offshore parts of the gulf after the end of April, for it was detected at only one station 
off Cape Elizabeth (10277) during the May cruise of the Grampus in 1915, not at all 
at the 10 stations occupied by the Albatross on the western side of the gulf and on 
Georges Bank from May 4 to 17, 1920 (stations 20120 to 20129). We have not found 
it at sea in the gulf during the summer and only once during the autumn, viz, off 
Penobscot Bay on October 9, 1915 (station 10329). 
Th. nitschioides follows much the same seasonal cycle in north European waters, 
where it flowers most abundantly from February until April, according to locality, 
diminishing in abundance during May, and with its annual minimum in August. 
It is far less important as a member of the plankton in the Gulf of Maine, where we 
have never found it abundant, than it is in the North Sea region, where it occurs at 
all times of the year (Ostenfeld, 1913, p. 409), very generally over the entire area, 
and at times in great numbers. 
The occurrence of Th. nitschioides so far offshore off Nova Scotia and over the 
southeastern slope of Georges Bank, contrasted with our failure to find it in any of 
