PLANKTON OF THE GULF OF MAINE 



413 



1 Numbers about equal. 



1 Predominant. 



» Fewer. 



> Not found. 



Just how rapidly O. tripos may be expected to spread eastward toward Cape Sable 

 from its offshore center of abundance in the center of the gulf is yet to be learned. 

 It is established, however, that on August 12, 1913 (station 10095), and again on 

 September 2, 1915 (station 10311), the two species were present in roughly equal 

 numbers on German Bank, where longipes alone was found in June, 1915 (station 

 10290). Tripos greatly outnumbered longipes near Lurcher Shoal (station 10245) 

 and in the neighboring part of the basin (station 10246) as early as August 12 in 1914. 

 It is also probable that tripos will usually be found to dominate close in along the 

 west Nova Scotian coast before the middle of September, for it outnumbered longipes 

 near land off Shelburne (a few miles east of Cape Sable) on the 6th of that month in 

 1915 (station 10313, 30 tripos to 12 longipes), where we had found longipes predomi- 

 nant the previous June, 40 as well as during July and August of 1914. 41 



Ceratium tripos comes finally and definitely to dominate over C. longipes in all 

 parts of the gulf by the middle or end of October, including even the coastal belt east 

 of Penobscot Bay. McMurrich (1917) did not find longipes at all at St. Andrews 

 after the 16th of that month, whereas C. tripos occurred there regularly from that 

 date until March 2, when Ceratium disappeared with the inception of the vernal 

 flowering of diatoms. 



C. tripos has greatly outnumbered C. longipes in all the parts of the gulf we have 

 visited in midwinter; in fact, the latter, if not wanting, was at least so rare that I 

 failed to find it in several of the samples examined. 



Relative abundance of the several species of Ceratium in winter, from samples 



Locality 



C. lon- 

 gipes 



C. tripos 



C. fusus 



C.arcti- 

 cum 



Massachusetts Bay, Dec. 29, 1920, station 10488 



Off Cape Ann, Dec. 29, 1920, station 10489.. 



Western Basin, Dec. 29, 1920, station 10490 



Off Cape Cod, Dec. 30, 1920, station 10491... 



Off Merrimac River, Dec. 30, 1920, station 10492 



Off Isles of Shoals, Dec. 30, 1920, station 10493. 



Off Cape Elizabeth, Dec. 30. 1920, station 10494.. 



Off Penobscot Bay, Jan. 1, 1921, station 10496 



Off Mount Desert Island, Jan. 1, 1921, station 10497 



Off Machias, Me., Jan. 4, 1021, station 10498 



Fundy Deep, Jan. 4, 1921, station 10499 



Eastern Basin, Jan. 4, 1921, station 10500 



Eastern Basin, Jan. 5, 1921, station 10502 



Off Yarmouth, Nova Scotia, Jan. 4, 1921, station 10501. 



" Station 10291, 19 longipes, 1 tripos; station 10294, many longipes and intermediates between it and nrcfica, no tripos. 

 " Station 10232, July 28, many longipes, no tripos; station 10233, July 28, 42 longipes, 3 tripos; station 10243, August 11, many 

 longipes, no tripos. 



