PLANKTON OF THE GULF OF MAINE 



463 



circumscribed areas in which it occurs when it does swarm and the suddenness of its 

 appearances and disappearances, the causes of which are totally unknown. 



TINTINNIDS 



The tintinnids of the Gulf of Maine offer an interesting field for study because 

 the several members of Cyttarocylis — the chief genus — have rather precise geo- 

 graphic characteristics (Jdrgensen, 1S99; Brandt, 1906). The records for 1914, 1915, 

 1916, and 1920 show that tintinnids may be expected anywhere in the gulf; only 

 rarely, however, have they formed any considerable part of our catches of phyto- 

 plankton. As a rule, they are decidedly scarce, often absent, or at least so rare as 

 to be overlooked, though they are conspicuous objects in the field of the microscope. 

 Inl920 they were found at most of the March stations in the eastern side of the gulf 

 from the coast of Nova Scotia cut to the Eastern Channel and across the continental 

 slope off Cape Sable (fig. 133; tintinnids sufficiently numerous to be recorded at 

 stations 20071, 20072, 20074 to 20079, 200S3, 200S4, and 200S6) ; but none were 

 detected on Georges Bank or in the western halt of the gulf during that month. 

 By mid-April " the tintinnids, like the peridinians, had practically disappeared frcm 

 the waters where they occurred in March, with no compensating augmentation else- 

 where in the gulf. In 1915 we found tintinnids in some numbers on German Bank 

 and off Lurcher Shoal on the 7th and 10th of May (stations 10271 and 10272), as 

 well off as Penobscot Bay two days later (station 10276). Apparently (though our 

 records are insufficient) they gradually spread westward from May on, with the ad- 

 vance of the season, for we took them in large numbers off Cape Cod on July 22, 

 1916 (station 10346). 



In August and September, 1915, tintinnids were recognized in the Eastern Basin, 

 in the center of the gulf, and alongshore from Penobscot Bay to Cape Elizabeth 

 (stations 10304 to 10306, 10310, 10311, and 10316 to 10319). In October of that year 

 they occurred in localities as widely separated as the Massachusetts Bay region (stations 

 10320, 10323. and 10336), the neighborhood of Mount Desert Island (station 10328), 

 and off the Grand Manan Channel (stations 10316 and 10327). McMurrich found 

 them at St. Andrews from late August until October 9, in 1916. In short, they may 

 be expected anywhere in the gulf in summer and early autumn. 



Only three times have we found tintinnids an important factor in the plankton 

 of the gulf — that is, at the Cape Cod station just mentioned, July 22, 1916, where 

 there were about half as many Cyttarocylis as Ceratium in a sample taken at random; 

 off Cape Elizabeth on September 20, 1915 (station 10319); and off the southeast 

 slope of Georges Bank on July 22, 1914 (station 10220). But the group is evidently 

 more important east of Cape Sable, for they appear at times in great numbers in the 

 cold water along the outer coast of Nova Scotia, this being the case at several of our 

 stations in July and August, 1914 (Bigelow, 1917, p. 329). Wright (1907) records 

 both Tintinopsis and Cyttarocylis as common at Canso, Nova Scotia, during the 

 summer. 



' ; There are only two April records for the group in the gulf— stations 20098 and 20101. Elsewhere during that month they 

 were at least so rare as to be overlooked. 



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