450 



BULLETIN OF THE BUREAU OF FISHERIES 



of an eastward expansion of its flowering area; and although the waters farther east 

 along the coast supported only a scattering of Thalassiosira on the 12th (station 20099, 

 April 12), it is probable that this genus is flowering actively all along the northern 



Fig. 129.— Distribution of the diatom genera Thalassiosira and Lauderia glacialis. O. locality records for Thalassiosira for 

 March; X. for April; O. for Lauderia glacialis. The hatched curve marks the offshore boundary to the abundant 

 flowerings of Thalassiosira up to mid-March; the stippled curve incloses its flowerings up to the last week of April for 

 the years 1913 and 1920 



shores of the gulf by the middle of the month in most years. It is also likely that 

 the harbors and bays along this part of the coast see a great production of Thalas- 

 siosira commencing a week or two earlier, judging from conditions at St. Andrews. 



