PLANKTON OF THE GULF OF MAINE 441 



waters as a whole (Ostcnfeld, 1913), but its rarity or absence in the inner parts of 

 the Gulf of Maine contrasts sharply with its status in European coastal waters, 

 such as the English Channel and the North Sea generally, where it is one of the 

 most dominant of diatoms. This difference in its distribution in the two sides of 

 the North Atlantic can not be explained until its life history is better known for 

 American waters, but it is at least suggestive that Guinardia flowers chiefly at a 

 time of year when the Gulf of Maine oilers the least favorable environment for the 

 multiplication of diatoms of any sort. 



Lauderia 



The brief dominance of Lauderia glacialis off the coast of Maine in the very 

 scanty pelagic flora of early March (stations 20056 and 20058) prior to the flowering 

 of Thalassiosira has already been mentioned (p. 421), as has its occurrence near Cape 

 Ann and in Massachusetts Bay at that same season (stations 20060 to 20062). 

 In the western side of the gulf the flowering of Lauderia probably reaches its cul- 

 mination by the end of March, at the latest, for it was not detected at any of the 

 April stations west of Mount Desert in 1920. It is later in appearing in the eastern 

 side of the gulf, for while none were detected at our several stations off western 

 Nova Scotia on March 23, 1920, it was present there and out to the eastern chan- 

 nel and the southeast face of Georges Bank by April 15 and 16 (stations 20101, 

 20107, and 20109), accompanying the early flowerings of Chsetoceras and Thalas- 

 siosira, though nowhere abundant. 



Thus Lauderia appears just prior to the rich vernal flowerings of Thalassiosira 

 and Chsetoceras, reaches its maximum while these two genera are still in a state of 

 active multiplication, and diminishes or vanishes after the brief period of a few 

 weeks while they are still swarming. We have occasionally found Lauderia among 

 other diatoms in May (station 10285 in 1915), but it is not recorded for later sum- 

 mer or autumn. Neither McMurrich (1917), Bailey (1917), nor Fritz (1921) have 

 detected it at St. Andrews or in the Bay of Fundy. L. glacialis (fig. 117; Gran, 

 1908, p. 23, fig. 23) is the basis of all our records for the genus. 



Nitschla 



NitscJda seriata, like Skeletonema costatum (p. 448), is a summer species in the 

 Gulf of Maine, where it has not been detected during the spring months. Our 

 earliest seasonal record of it is for June 10, when it was represented by occasional 

 examples among the more abundant Chastoceras and other genera off Petit Passage, 

 Nova Scotia, in 1915. Fritz (1921) found it constantly at St. Andrews from July 

 3 onward throughout the summer; Bailey (1917) records it from the Bay of Fundy 

 in August; and it has appeared with comparative regularity in our July and August 

 tow nettings in those parts of the gulf where diatom plankton persists so late in the 

 season, more especially in the coastal belt between Cape Elizabeth and Nova Scotia. 

 For example, N. seriata was present in fair quantity on Jeffreys Bank off Penobscot 

 Bay, as well as close in to the land nearby (stations 10016 to 10021 and 10025), 



FROM THE 



ARCHIVES 



THE 



WOODS HOLE OCEANOGRAPHIC INSTITUTION 

 WOODS HOLE. MASSACHUSETTS 



