PLANKTON OF THE GULF OF MAINE 285 



the gulf in spring and early summer than at other seasons, or whether it has been 

 an accidental feature of the towings. 



It should be noted that the presence of R. nasutus in the Gulf of Maine at any 

 particular temperature or salinity does not necessarily bear any relation to the range 

 of these factors in which it finds its most favorable environment, but simply means 

 that once swept into the eastern side of the gulf by the entrant eddy it has been able 

 to survive long enough to drift to the place where found. The present records prove 

 such survival possible for a time in water as cold as 2 to 3° (stations 20072 and 20095) 

 and in salinities no higher than 29.16 to 31.36 per mille (station 20120), though its 

 usual range in the open North Atlantic is nearly if not wholly limited to salinities 

 higher than 34.9 per mille, and for the most part to regions where the wat.v is warmer 

 than 10° at some level. Geographic distribution suggests that R. nasutus finds tem- 

 peratures and salinities appreciably lower than these figures an effective preventative 

 to successful reproduction. 



The records for R. nasutus within the gulf have invariably been for small num- 

 bers of specimens, in three cases for single individuals noted in the catch of copepods 

 (designated "T" (trace) in the accompanying tables), and only once for as many 

 as 550 per square, meter (station 20120). It has invariably been a minor element 

 (5 to 10 per cent) in the copepod community, even along the continental slope, 

 where it occurs more constantly, with a maximum abundance of about 1,000 to 4,000 

 per square meter (stations 20045 and 20069). 



Scolecitliricella minor (Brady) 



This species has its chief center in the North Atlantic and neighboring Arctic 

 seas. In the northerly part of its range it has been found along the Norwegian coast 

 as far as Lofoten; at many localities, but usually in small numbers, between Spitz- 

 bergen and Greenland northward to latitude 80° 17' N.; and generally distributed 

 about the Faroes and Iceland, in Denmark Strait, off southern Greenland, and north- 

 ward to latitude 64° 54' in Davis Strait (see With, 1915, for a summary of the records 

 for this species so far published). 



The Michael Sars did not find it off the western slope of the Grand Banks, but 

 the Canadian fisheries expedition had it at six stations outside the continental edge 

 at the mouth of the Laurentian Channel between Banquereau and Green Bank, off 

 Sable Island, and off Cape Sable; also twice in the Gulf of St. Lawrence (Willey, 

 1919), and there are a few records for it in the Gulf of Maine, to be noted below. It 

 has not been reported south of Cape Cod in the western Atlantic. In the eastern 

 Atlantic it is common west of Ireland (Farran, 1905 and 1908), and while not known 

 in the Mediterranean or anywhere in the north-central Atlantic, it was found by T. 

 Scott (1894) in two samples from the Gulf of Guinea, one of them taken so close in 

 to the mouth of the Congo River that the water was visibly brownish. S. minor 

 has not been reported either from the South Atlantic, the Pacific, or from the tropical 

 part of the Indian Ocean, but the original specimens of the species were from the 

 subantarctie zone of the latter, west of the Crozet Islands, in latitude 46° 46' S., 

 longitude 45° 31' E., in a surface haul. 



