PLANKTON OF THE GULF OF MAINE 365 



Eastport, one specimen, summer of 1S85 (Fewkes, 1888, p. 235); and Western Basin, 

 March 24, 1920, 200-0 meters, Albatross station 20087. 



Dactylometra quinquecirrha, a southern species, is fairly common as far east and 

 north as the Woods Hole region, but has never been taken past Cape Cod. 



The bathypelagic Periphylla Jiyacinihina has been credited to Georges Bank. 7 

 Actually, however, the specimens in question were taken off the southeast slope of 

 the latter well out beyond the 500-meter contour (Smith and Harger, 1874, p. 52, 

 as " Cliarybdea hyacinthina"). Pelagia cyanetta and the large tropical rhizostome 

 Stomolophus meleagris have been reported just outside the 100-meter contour south 

 of Marthas Vineyard (Fewkes, 1886, and Hargitt, 1905a), and the cruises of the 

 Albatross from 1883 to 1885 yielded a considerable list of tropical and bathypelagic 

 scyphomedusae (including Periphylla) outside the edge of the continent abreast of 

 the Gulf of Maine (Smith and Harger, 1874; Verrill, 1885; Fewkes, 1886). How- 

 ever, except as just noted, none of these have ever been taken inside the 500-meter 

 contour off the offshore banks of the gulf or within the latter. 8 



Ctenophores 

 Pleurobracliia pileus (Fabricius) 



From the economic standpoint the .ctenophore Pleurobrachia pileus 9 is the most 

 important pelagic ccelenterate inhabiting the Gulf of Maine, for not only is it ex- 

 tremely voracious and locally abundant beyond all computation, but it is present 

 there throughout the year, not for only a brief season annually, as are Aurelia 

 (p. 362) and Cyanea (p. 357). 



The abundance in which Pleurobrachia appears in Massachusetts Bay and 

 elsewhere along the New England coasts in summer and early autumn has often 

 been referred to in literature, but practically nothing was known of its occurrence 

 in the gulf at any other season until the recent systematic exploration was under- 

 taken. During March and April (which is a natural starting point in the seasonal 

 history of any planktonic animal, being the time when vernal warming makes itself 

 felt) we have found Pleurobrachia occurring very generally all around the periphery 

 of the gulf from Cape Cod to Cape Sable (fig. 101), but so closely confined to shoal 

 water that we took it only twice outside the 100-meter contour- in the inner parts 

 of the gulf in 1920 and not at all in the basin of the gulf except for the extreme north- 

 eastern corner. Nor did we find it on Georges Bank at any of our February, March, 

 or April stations, though it was plentiful on Browns Bank on March 13 (station 20072) 

 and again on April 16 (station 20106). 



Our experience in 1915 suggested that Pleurobrachia remains confined to the 

 shoal periphery of the gulf until well into May, if not later, as I have previously 

 noted (Bigelow, 1917, p. 304), but we found it in abundance on the southwestern 

 part of Georges Bank and less plentifully off the seaward slope of the latter on the 

 17th of that month in 1920 (stations 20128 and 20129), where there had been none 



' I foil into this error myself (Bigelow, 1914b, p. 27). 



' Pee also page 67 for a list of bathypelagic medusas from our outermost station off Shelbourne, Nova Scotia, Mar. 19, 1920 

 (station 20077), and page 54 for tropical coelenterates at the outer station oil Oeorges Bank, July 21, 1914 (station 10218). 

 • For a description, with beautiful figures of the adult, see L. Agassu, 1849. Mayer (1912) gives a more recent account. 



