PLANKTON OP THE GULF OF MAINE 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 Ilf, 1915, and 
“Albatross” cruise, May 1 to 17, 1920 1 
Locality 
C . tripos 
C. Ion 
gipes 
C. arctica 
C. fusus 
1 
30 
0 
0 
1 
39 
8 
4 
2 
12 
1 
1 
Eastern Basin, 1915: 
0 
30 
5 
1 
0 
20 
1 
1 
0 
100+ 
100+ 
6 
0 
1 
18 
0 
North of Cape Ann, 1915, station 10278. 
0 
12 
1 
0 
Southwestern Basin, 1920, station 20127 
1 
10 
0 
0 
25dh 
25+ 
0 
1 
Southern edge of Georges Banks, 1920, Station 20129 
0 
25± 
0 
0 
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 
C. tripos 
C. lon- 
gipes 1 
C. arctica 
C. fusus 
3 
100+ 
9 
0 
1 
0 
0 
0 
( 2 ) 
4 
( s ) 
19 
0 
0 
0 
o 
1 Including occasional intermediates between it and arctica. 3 Swarm. 
1 Occasional. 
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. 328, 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 
31 At one station (10301) off the mouth of the Grand Manan Channel, July 15, 1915, there were 16 longipes to 3 tripos. 
