416 
BULLETIN OF THE BUREAU OF FISHERIES 
occurs in any numbers, and at all seasons , 42 both in the inner parts of the gulf, on 
Georges Bank, on Browns Bank, and off southern Nova Scotia (Bigelow, 1917, p. 
323). It has been lacking, or at least so rare as to be overlooked, whenever diatoms 
swarm, in which it parallels the more abundant species, tripos and longipes; occasion- 
ally, also, among catches of Ceratium plankton. However, no more definite seasonal 
fluctuation in abundance has been established for it in the Gulf of Maine, nor any 
regional concentration. Notwithstanding its nearly universal distribution in the 
gulf and almost constant occurrence there, it seldom rivals the tricornuate forms of 
Ceratium in abundance, the only instance of this sort so far recorded being that 
C. tripos and C.fusus were about equally numerous in the center of the gulf on August 
10, 1913 (Bigelow, 1915, p. 334, station 10090). 
The sporadic occurrence of the tropical species, C. macroceras, in the inner 
parts of the gulf has already been alluded to (p. 393). C. buceplialum (Paulsen, 1908, 
p. 77, fig. 100) has also been recognized once in early spring (mouth of the Bay of 
Fundy, station 20079, March 22, 1920); likewise off the southeast face of Georges 
Bank on February 22, 1920 (station 20044), and south of Marthas Vineyard, Novem- 
ber 11, 1916 (station 10406). 
Other peridinians 
Only two other genera of peridinians have so far been definitely recognized in 
the Gulf of Maine — Peridinium and Dinophysis — though others doubtless occur. 
The former has been noted in practically every summer sample in which Ceratium 
occurs (Bigelow, 1915, p. 334); that is, it is practically universal in the gulf except 
in regions and at times where diatoms flower abundantly, (and even there it may be 
present but overshadowed by their masses) or when the plankton is so scanty that 
it may have been overlooked, though actually present, as, for example, at several 
of our stations in the early spring of 1920. Peridinium is usally a minor element in 
the phytoplankton; far less numerous than its companion genus Ceratium. In 
summer and early autumn the only exceptions to this rule have been on the western 
part of Georges Bank, July 20, 1914 (stations 10215 and 10216); near Mount Desert 
Island, September 15, 1915 (station 10317); and off Penobscot Bay, October 9 of that 
same year (station 10329), where the genus as a whole (represented by several species) 
was nearly as numerous as either species of Ceratium. Peridinium is relatively 
even less important in early spring, as exemplified by our cruises of March and April, 
1920, when it was represented by few or occasional examples only, though it occurred 
at about half the stations, distributed over the gulf generally 43 except in the rich 
diatom centers. In May of 1915, however, Peridinium not only occurred at every 
station where Ceratium was detected, but rivaled the latter in abundance in the 
eastern side of the gulf (fig. 115, stations 10270, 10272, and 10273). 
As it was again an important element in the plankton of the southwestern part 
of the basin and of the South Channel on May 17, 1920 (stations 20127, 20128, and 
« For records of its occurrence in the summer hauls of 1913 and 1914 see Bigelow, 1915, p. 333, and 1917, p. 323. During the 
autumn of 19J6 it was recognized at stations 10400 to 10406; during the spring of 1920 at stations 20044 to 20046, 20048, 20049, 20052 to 
20065, 20057, 20063 to 20005, 20067, 20068, 20070 to 20074, 20077, 20080, 20086, 20087, 20093, 20096 to 20098, 20101, 20108, 20111, 20112, 200116, 
20118, 20125, and 20128; and at all the stations during December, 1920, and January, 1921 (stations 10488 to 10502). 
43 Recorded for stations 20044, 20045, 20046, 20048, 20057, 20060, 20064, 20065, 20068, 20071, 20074, 20075, 20080, 20086,20088,20089, 
20096, 20111, 20118, and 20119 for these months. 
