PLANKTON OF THE GULF OF MAINE 



423 



chusetts Bay and of the former in the Bay of Fundy late in summer and early in 

 autumn (p. 394). Fish (1925) has already called attention to the interesting fact 

 that these, which are summer forms in Massachusetts Bay to the north of Cape Cod, 

 dominated the December catch at Woods Hole. The winter (lowering of lih. aJata 

 in Capo Cod Bay, described above (p. 396), is also interesting because suggesting a 

 more southerly seasonal cycle there than for other parts of the gulf. 



The accompanying photographs (figs. 117 to 126) illustrate the actual associa- 

 tions of the various species of diatoms in different parts of the Gulf of Maine from 

 season to season. Several representative lists for standard stations also follow. 

 The reader is cautioned, however, that in no case do these pretend to be complete, 

 only the more numerous forms, such as would be found by examining a fair sample 

 (but without exhaustive search) , being enumerated. Whenever the genus Chaetoceras 

 forms any considerable part of the total plankton it has comprised specimens (listed 

 as Chaetoceras sp.) the identit} 7 of which has not been determined for one reason or 

 another. But this limitation does not interfere seriously with the value of the lists, 

 for it is precisely the more common and therefore ecologically more important species 

 that are of interest to the student of broad oceanographic and biological problems. 

 The samples for each station were examined independently by Dr. Albert Mann 

 and by me unless otherwise noted. Species verified by Doctor Mann are starred. 

 Since no attempt is made to contribute to the systematics of the group, the nomen- 

 clature follows Gran's (1908) convenient manual of the planktonic diatoms of northern 

 seas, except in the genus Coscinodiscus, where Doctor Mann recognizes the older 

 species, asteromphalus Ehrenberg and oculus-iridis Ehrenberg, as distinct from sub- 

 bulliens Jorgensen. 



Lists of diatoms at representative localities 



[The most plentiful species for each station are so designated by being located above the dotted line. Species of which only 

 odd examples were noted are marked S. The presence of the starred (*) species was verified by Dr. Albert Mann.] 



1. — Massachusetts Bay 



A. Southwest side Cape Cod Bay, November 



12, 1925 (Fish Hawk, trip 1, station 9) : 

 Diatoms scarce. 49 

 Rhizosolenia alata dominant. 



Chaetoceras boreale. 

 Ch. decipiens. 



B. Center of Cape Cod Bay, February 7, 1925 



(Fish Hawk, trip 6, station 7) : 

 Diatoms abundant. 49 

 Rhizosolenia alata dominant. 



Chatoceras decipiens. 

 Ch. boreale. 

 Coscinodiscus sp. 

 Thalassiosira nordenskioldi. 

 Thalassiothrix longissima. 

 <» Identified by Dr. C. J. Fish. 



C. West of Stellwagen Bank, February 28, 1925 



(Fish Hawk, trip 7, station 2) : 

 Diatoms very abundant. 48 

 Thalassiosira nordenskioldi dominant. 

 Thalassiothrix longissima abundant. 



Biddulphia aurita. 

 Chaetoceras atlanticum. 

 Ch. decipiens. 

 Coscinodiscus sp. (?). 

 Rhizosolenia alata. 

 Rh. semispina. 

 Thalassiothrix nitschioides. 



D. Off Gloucester, March 1, 1920, station 20050: 



Diatoms scarce. 



Chaetoceras decipiens dominant. 

 ♦Thalassiosira nordenskioldi dominant. 



