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B02 BULLETIN: MUSEUM OF COMPARATIVE ZOOLOGY. 
likewise more diatoms at our other stations near land than in the ~ 
centre of the Gulf; but not enough to take the hauls out of the 
Ceratium class. The diatom constituents of the Gulf Stations were 
chiefly several small species of Chaetoceras, with occasional C. de- 
cipiens, Rhizosolenra semispina and Nitschia serriata, ete. 
Peridinian plankton, in greater or less abundance, and composed 
of different species at different localities, occupied the waters of the 
Gulf of Maine (Stations 10057, 10086-10093, 10096, 10097, 10102, 
10104) except at the few limited regions just mentioned; Nantucket 
Shoals (Staton 10060), the continental shelf from abreast of Nantucket 
to New York (Stations 10062, 10063, 10067, 10082, 10083, 10070) 
(Fig.82). Unfortunately we have no data on the microplankton of the 
Gulf Stream water at Station 10076, the bottle being broken in transit. 
In the Gulf of Maine the prevalent organisms, of this plankton type, 
were two species of Ceratium, tripos, and the form classed by Paulsen 
(1904, 1908), as var. oceanica of C. longipes. (In my Report on the 
cruise of 1912, these two species were treated together). Ceratiwm 
longipes differs so noticeably from tripos in its curved apical horn and 
serrate shell, that it is easy to count the respective numbers of the 
two in plankton samples. And without delaying with the exact 
counts, the result of the comparison was as follows :— 
Roughly equal num- 
Longipes outnum- bers Tripos and Tripos outnum- 
bers tripos longipes bers longipes 
Stations 10057 Stations 10058 Stations 10088 
10059 10090 10089 
10087 10092 
10091 10093 
10098 10095 
10102 10096 
-10103 10099 
10104 10105 
On the whole, then, longipes was the more abundant of the two in 
the Gulf, where it was taken at practically every station, though 
notably absent at Station 10086, where it had been abundant a month 
earlier (Station 10057). The table likewise suggests that the prepon- 
derance of longipes was greater near shore than in the centre of the 
Gulf, the only stations where tripos predominated being far from land. 
C. longipes occurred in the plankton on George’s Bank, on Nan- 
tucket Shoals, and over the continental shelf as a whole as far as 
