PLANKTON OF THE GULF OF MAINE 307 



Oncsea conifera. — Twelve specimens, including both sexes, were taken at the 

 surface in the Eastern Channel, April 16, 1920, station 20107. 



Oncsea minuta. — Fifteen males and females were captured in a vertical haul in 

 deep water southeast of Georges Bank, March 12, 1920, station 20069. 



Oncsea venusta. — Twenty-five males and females were found in a vertical haul 

 south of Georges Bank, February 22, 1920, station 20044, 



Scolecithricella obtusifrons. — Three females were captured in a vertical net in 

 deep water southeast of Nova Scotia, March 19. 1920, station 20077. 



Scolecithricella ovata. — Twenty females were taken in a vertical net south of 

 Georges Bank, February 22, 1920, station 20044. 



Temora stylifera. — A single female was captured in a vertical net southeast of 

 Nova Scotia, September 6, 1915, station 10313. 



Tisbe furcata.—A single female was taken at the surface just outside Boston 

 Harbor, April 6, 1920, station 20089. 



Daphntds (Cladocera) 



These little crustaceans are often extremely plentiful in the coastwise waters 

 of boreal seas, especially of the North Sea region. It is probable that they are an 

 important element in the plankton of estuarine situations all around the coast line 

 of the Gulf of Maine, for McMurrich found the genera Podon and Evadne regularly 

 at St. Andrews during the summer months, often in abundance, while to the south 

 of our area Fish (1925) reports both Evadne and Podon in abundance at Woods Hole 

 and in Long Island Sound. The group as a whole, however, is so strictly neritic 

 that it hardly figures in the planktonic communities of the open gulf more than a 

 few miles out from land, except at rare intervals for brief periods, and is only acci- 

 dental outside the 100-meter contour. 



Only one cladoceran genus — Evadne — has yet been noted in our catches, and 

 because of its slight importance in the natural economy of the offshore waters of 

 the Gulf of Maine no attempt was made to list the occurrence in the towings of 

 1912 to 1914. A preliminary survey of the surface towings for 1915 located it at 

 stations 10287, 10302, 10303, 10313, 10317, 10318, and 10319 and in Shelburne Har- 

 bor, Nova Scotia. In 1916 Evadne was recorded at only one Gulf of Maine station — 

 10398. All these localities, as I have already stated (p. 35), lie within 15 miles 

 of land. It did not appear in the samples of the catch at the other summer sta- 

 tions, which were passed under the microscope, but as examination of larger amounts 

 of the plankton might have disclosed occasional specimens of Evadne, the most that 

 can be said is that it was certainly scarce if not actually absent at the stations where 

 it was not recorded (also on Georges Bank, August 13, 1926). 



Evadne was not found at all in the spring towings of 1920 or during the winter 

 and early spring of 1920-1921, but in August, 1922, it appeared at several stations 

 in Massachusetts Bay (10636, 10637, 10638, 10640, 10641, 10643, and 10644). Up 

 to that time we had found it in large numbers on only two occasions, namely, 

 near Cape Elizabeth, September 20, 1915 (station 10319), and Cape Cod Bay, August 

 24, 1922 (station 10644), most of the other records being based on only a scattering. 

 On August 18, 1924, however, after this report was ready for the press, surface tows 



