334 bulletin: museum of comparative zoology. 



where diatoms swarmed (i. e., George's Bank, the mouth of Chesa- 

 peake Bay, and near Mt. Desert Island). And even then its absence 

 from the plankton samples examined may be accidental, because there 

 are a few other stations also where I failed to find it in the tow. It 

 was outnumbered by the other species of the genus everywhere, except 

 at one station in the centre of the Gulf of Maine (10090) where there 

 were about equal numbers of tripos, longipes, and fusus in a sample. 



Two other genera of peridinians may be mentioned briefly. Peri- 

 dinium occurs in practically every sample in which Ceratium has 

 been noted, being absent only in the Gulf Stream hauls (Stations 

 10071, 10073), off Chesapeake Bay (Stations 10075, 10076, 10077, 

 10078, 10079), and in the diatom plankton found off Mt. Desert. One 

 species, provisionally identified from Paulsen's account (1908) as 

 P. crassipes Kofoid occurs over the whole range of stations, except as 

 above; but always in small numbers. Two other species, oceanicum 

 at Station 10062 and 10070; paUidum at Stations 10063, 10067 and 

 10090, have likewise been detected so far. And additional records 

 for these, and other species, may be expected when the microscopic 

 examination of the microplankton is completed. 



The genus Dinophysis is represented by two species, ovum (noted 

 only twice) and norvegica; the latter being of considerable importance 

 from the oceanographic standpoint, because it was found only in the 

 Gulf of Maine (Stations 10090, 10096, 10097), and because of its 

 northern distribution in general (Paulsen, 1908). 



The hauls made in 1913 were not of a type calculated to reveal the 

 exact quantitative amount of plankton in the water; for this purpose 

 vertical hauls with a quantitative net must be resorted to. But as 

 I have previously pointed out (1914a), the horizontal hauls do show 

 in a rough way whether the water is barren, rich, or intermediate 

 between these two extremes. 



Off Cape Cod, in early July (Stations 10057 and 10058) the micro- 

 plankton was rich: and this was likewise true south of Nantucket 

 (Stations 10062, 10063) ; on George's Bank (Station 10059) ; off Chesa- 

 peake Bay (Stations 10075, 10078); and near Mt. Desert Island 

 (Stations 10099, 10101). But nowhere, in 1913, was it found as dense 

 as it was in several places in the Gulf in 1912 (1914a). And as a rule 

 it was notably scanty, being so classed at Stations 10061, 10069-10073; 

 10079-10083^ 10086-10090; 10092, 10093, 10096, 10098, 10102, 

 10104, 10105; perhaps most barren of all at Stations 10071, 10081, 

 10082 and 10083. It was intermediate, quantitatively, at Stations 

 10060, 10065, 10067, 10074, 10077, 10091, 10095, 10097, 10103. 



