418 BULLETIN OF THE BUKEAU OF FISHERIES 



the various river mouths, bays, and harbors between Cape Cod and Grand Manan, 

 but McMurrich (1917), Bailey (1917), and Fritz (1921) have published extensive 

 lists of the diatoms occurring in the neighborhood of St. Andrews as well as at other 

 localities in the Bay of Fundy and its tributaries, and Fish (1925) has done so for 

 Woods Hole diatoms. 



The survey of the diatoms, like that for the peridinians (p. 407), may commence 

 at the end of the winter or first days of spring. At this season, as exemplified by the 

 cruises of the Albatross during February and March, 1920, the diatom communities 

 of the gulf fall naturally into three groups, according to locality — 1, the sparse diatom 

 flora of the whole deep basin and of the eastern half of the gulf from the mouth of the 

 Bay of Fundy and the Nova Scotian coast on the one side to Cape Cod on the other, 

 and from the 100-meter contour on the north to the shallows of Georges Bank on 

 the south (p. 383) ; 2, the rich area on the western part of Georges Bank (p. 385) ; and 3, 

 an even more productive zone along the western shore of the gulf (p. 383). 



Over all the considerable expanse of the first area, noted on the chart (fig. 104) 

 as "sparse mixed", Coscinodiscus (mingled with peridinians, as I have noted 

 above) is the dominant diatom genus in March (dominant, however, not so much 

 for its own numbers as for the scarcity of anything else) , with the easily recognized 

 C. asteromphalus (p. 437) its chief though not its only representative at that time. 

 At most of the March stations offshore the three species of Chsetoceras — C. decipiens, 

 C. atlanticum, and C. criophilum — were likewise practically universal in the gulf in 

 1920. 47 These three are all oceanic in nature (Gran, 1908 and 1912; Ostenfeld, 1913) ; 

 such, likewise, are Chsetoceras densum, Rhizosolenia semispina, and R. styliformis, 

 which have been detected at 5, 12, and 2 of the February and March stations in 1920. 

 The offshore hauls likewise yielded an unmistakable if minor component of neritic 

 origin, contributed by the coastal belt or by the offshore banks, including the follow- 

 ing species: Chsetoceras debile, Ch. didymum, Ch. diadema, Ch. mitra, Ch. sociale, 

 Ch. laciniosum, Ch. contortum, Biddulphia aurita, Eucampia zodiacus, Licnophora, 

 Lauderia glacialis, 48 Thalassiothrix nitsehioides, Skeletonema, and Thalassiosira. 

 Thalassiothrix longissima, which is partly oceanic and partly neritic on the other 

 side of the Atlantic (Ostenfeld, 1913), was likewise detected just north of Georges 

 Bank (station 20064) and on its eastern part (station 20066) on March 11. 



When the occurrence of these several neritic forms is plotted for March, 1920 

 (fig. 116), it is evident (as might be expected) that they were most abundant around 

 the periphery of the gulf, and especially in its western side between Massachusetts 

 Bay and Portland, where diatoms were flowering actively at the time (p. 383) ; very 

 rare, indeed, in the central deeps of the gulf, to whose diatom flora neither the coast 

 line nor the shallow banks were contributing appreciably. It is interesting that this 

 was equally true of the eastern part of Georges Bank in that March, though neritic 

 diatoms swarm there at other seasons (p. 391). 



« These three species were detected side by side at 21 stations for February and March, 1920 (stations 20044 to 2004(3; 20048 to 

 20050, 20053, 20057, 20061 to 20060, 20071 , 20082, 20080, 20088) ; decipiens and criophyllum at stations 20070, 20078, 20079, 200S8; atlanticum 

 and criophyllum at station 20052; atlanticum and decipiens at stations 20056 and 20083; atlanticum only at station 20054; and decipiens 

 only at stations 20058, 20059, 20060, 20072, and 200S4. 



48 This species is well described and figured by Gran (1908), but Dr. Albert Mann, in a letter, remarks that several other diatoms 

 are confused under the synonyms there given. 



