PLANKTON OP THE GULF OF MAINE 283 
have been uniformly distributed vertically, the numbers present per cubic meter 
of water work out as follows for our richest catches of the species : 
Station 
Date 
Number 
Station 
Date 
Number 
10092 
Aug. 11,1913 
Aug. 12,1913 
do. 
119 
10332 
Oct. 21, 1915 
958 
10095. 
666 
10333 
Oct. 22, 1915 
382 
10096 
330 
10336 __ 
Oct. 26,1915 
Oct. 27,1915 
287 
10097 „ 
Aug. 13,1913 
306 
10338 
306 
RMncalanus cornutus Dana 
This species has its center of distribution in the Tropic belts of the three great 
oceans. It has been described from the Sulu Archipelago, from the Philippines 
(Brady, 1883), and from the western Pacific between latitudes 7° S. and 15° N. 
(Giesbrecht, 1892). It is common in the Malay Archipelago (Cleve, 1901; A. Scott, 
1909). Thompson and Scott (1903) had it at ten stations in the Indian Ocean; 
A. Scott (1902) reports it from the Red Sea; but up to the present I have found 
no record of it in the Mediterranean. The German South Polar expedition found it 
widespread in the South Atlantic (Wolfenden, 1911). To the northward it is reported 
from the equatorial belt off Africa; from the Gulf of Guinea, where T. Scott (1894) 
found it one of the most common and widely distributed species; and in the eastern 
side of the Atlantic at a few stations up to latitude 52° (Thompson, 1903). The 
only previous report of it on the American side is from one station outside the con- 
tinental edge off Cape Sable by the Canadian fisheries expedition, July, 1915 (Willey, 
1919). So far as eastern North American waters are concerned, the true home of 
this species lies well outside the continental edge, in almost Tropic temperatures and 
high salinities. 
In the Gulf of Maine this species is an accidental stray, appearing in the lists 
for nine hauls, including both horizontals and verticals (fig. 72; tables, p. 298-305), 
the captures within the gulf being in the northeastern part of the basin, off Penobscot 
Bay, off Cape Elizabeth, off the Merrimac River, and in Massachusetts Bay, a 
localization along the northern and western shores which parallels the distribution of 
other immigrants. There are also two station records for it on the continental 
shelf off Marthas Vineyard. 
Two of the records for R. cornutus in the inner part of the gulf are for March, 
two for September, and thrive for December. Evidently it may enter at any time of 
year, and is about as apt to do so at one season as another. The records off Marthas 
Vineyard were for October 21 and 22, 1915 (table, p. 298). 
There is no reason to suppose that this copepod is able to breed successfully 
within the gulf or to establish a permanent foothold there, the records from within 
the gulf all being for scattering specimens, up to a frequency of about 455 per square 
meter off Massachusetts Bay, September 29, 1915 (station 10321), at most 2 per 
cent of the copepods. Off Marthas Vineyard, however, the vertical haul yielded 
about 2,000 per square meter at one station (10333). 
