PLANKTON OF THE GULF OF MAINR 



409 



water from the Nova Scotian current (then near its maximum flow for the year), 

 which corresponds to a northern extralimital origin. 



Relative abundance of species of Ceratium in samples, "Grampus" cruise, May 4 to 14, 1915, and 



"Albatross" cruise, May 1 to 17, 1920* 



Locality 



Off Cape Ann, 1920, station 20124 



Oil Cape Ann. 1915, staton 102'X>_ 



Ofl Cope Cod, 1920, station 20125 



Eastern Basin, 1915: 



Station 10269 



Station 10270 



German Bank, 1915. station 1027K - 



09 Lurcher Shoal, 191S, station 10272 



North of Cape Ann, 1915, station 10278 



Southwestern Basin, 1920, station 20127 



\\ astern part ot Georges Bank, 1920, station 20128 



Southern edge of Georges Banks, 1920, Station 20129. 



C. fusus 



1 In this table no account is taken of the intermediates between C. arctica and C. longipes, although occasional examples of 

 this sort were noted at most stations, because it was usually possible to refer the specimens to one species or to the other. 



C. longipes continues the dominant species in the Gulf during the last half of 

 May and throughout the month of June, when peridinians play an increasingly 

 important role in the phytoplankton, as illustrated by the following counts of samples 

 for the year 1915: 



Locality 



Off Cape Cod, May 26, station 10279 



Oil Mount Desert, June 11, station 10284. 

 Southeast Deep, June 25, station 10298. . . 

 Western Basin, June 26, station 10299 



' Including occasional intermediates between it and arctka. 

 1 Occasional. 



1 Swarm. 



During this period C. arctica practically vanishes from the gulf, where our only 

 June record of it is in the extreme northeast corner (Bigelow, 1917, p. 32S, stations 

 10283, 10284, and 10286), and off Petit Passage in the southern side of the Bay of 

 Fundy (June 10, 1915). C. arctica has been detected only twice in the gulf in 

 the later summer or in autumn— that is, off Mount Desert, August 13, 1914 (Bigelow, 

 1917, p. 323, station 10248), and off Cape Ann, August 31, 1915 (station 10306) — 

 though it persists in some numbers along the southern coast of Nova Scotia at least 

 as late in the season as August (Bigelow, 1917, p. 323). 



C. tripos reappears in numbers in the Gulf of Maine tow nettings in July. 

 During the first half of that month, when the surface temperature of the gulf is 

 approaching its seasonal maximum and Ceratium its annual plurimum of abundance, 

 C. longipes has still predominated over C. tripos (usually markedly so) at almost all 

 the stations, both in the western half of the gulf generally, 38 over Georges Bank as 

 a whole, and across the whole breadth of the shelf abreast of southern Nova Scotia 

 (Bigelow, 1917, p. 323). Late in July, 1914, we found C. tripos dominating off the 



« At one station (10301) off the mouth of the Grand Manan Channel, July 15, 1915, there were 16 longipes to 3 iripo.'. 



