448 BULLETIN OF THE BUREAU OF FISHERIES 



Skeletonema 



SJcelteonema costatum is an interesting species because it reaches its maximum 

 abundance in the Gulf of Maine during the summer and early autumn, not in spring, 

 as most other diatoms do, whereas Fish (1925) found it a winter form at Woods Hole 

 and occurring only occasionally during the warm months. Skeletonema is typically 

 neritic and has been found flowering actively in Massachusetts Bay, the Bay of 

 Fundy, and on Georges Bank, but not in the deeper parts of the Gulf of Maine. 

 Bailey (1917) found it occasionally in estuarine situations on the north shore of the 

 Bay of Fundy in January and February and again in July and August, but not at all 

 during March, April, May, June, or October. In the open bay near Grand Manan 

 he describes it as abundant on September 18. Fritz's (1921) more extensive lists 

 note Skeletonema as occurring irregularly (always in small numbers) at St. Andiews 

 during the winter and early spring of 1917, multiplying in April, and reaching its 

 maximum in July and early August. In Massachusetts Bay we have not detected 

 it at all at any October, November, winter, spring, or early summer station, nor in 

 any of the hauls made in this region in 1916 — July, August, October, or November. 

 In 1915 it appeared at the mouth of the bay, near Provincetown, and off Cape 

 Cod from September 29 to October 1 (stations 10320 to 10323) in sufficient abundance 

 to give a characteristic aspect to the phytoplankton (p. 394), though the period of 

 reproduction must have been brief, for no Skeletonema were found at three stations 

 across the mouth of the bay on October 26 and 27 (stations 10337 to 10339). 



It would be interesting to know how far offshore this autumnal flowering ex- 

 tended, but unfortunately we have no data bearing on this. In 1922, however, when 

 it again dominated the phytoplankton at six stations around the shore of Massa- 

 chusetts Bay from Gloucester to the neighborhood of the Cape Cod Canal on August 

 24 (stations 10634, 10635 to 10637, 10639, 10642, and 10643), the belt that it occu- 

 pied extended only 4 to 5 miles out from land, none having been detected at the 

 eight other stations in the outer parts of the bay which the Halcyon occupied on that 

 day and two days previous. Unfortunately no plankton hauls were made later in 

 the season during that year. 



Skeletonema was also abundant on the western part of Georges Bank on July 9, 

 1913 (station 10059) — our only record of it on the offshore banks — among the Guiii- 

 ardia and Eucampia, which at the time dominated the local phytoplankton. The 

 only other records for it in the open gulf, outside the outer headlands, are for occa- 

 sional chains off Cape Sable, off Cape Cod, near Cape Ann, off Mount Desert Rock, 

 and in the northeastern corner of the basin in March and April, 1920 (stations 200S4, 

 20088, 20091, 20098, and 20100). 



Evidently the flowerings of this genus are closely confined to the immediate 

 vicinity of the land in the Gulf of Maine and to the shallow water of the banks, where 

 it flowers irregularly during summer and early autumn; and probably it will be found 

 to occur as abundantly along the coasts of Maine and Nova Scotia as it does in 

 Massachusetts Bay and at St. Andrews, when the diatoms of the other harbors and 

 bays are studied. 



Slceletonema costatum, a form of wide distribution, mainly northern, but, as 

 Ostenfeld (1913) remarks, including the coasts of almost all countries, is similarly 



