56 BULLETIN OF THE BUREAU OF FISHERIES 



Tropical pelagic, animals as conspicuous as Salpa and the Portuguese man-of- 

 war (Physalia), together with others less noticeable, are often carried close in to the 

 coasts of southern New England during the summer, west and south of longitude 

 70°, by sporadic movements of Gulf Stream water, with the topographic bight west 

 of Nantucket Shoals serving in particular as a trap for them, as the common occur- 

 rence of Physalia at Woods Hole and the considerable list of tropical pelagic fishes that 

 have been taken there (H. M. Smith, 1898; Kendall, 1908; Sumner, Osburn, and Cole, 

 1913) bear witness. Occurrences of this sort are far less frequent east of Cape Cod, 

 however, and when invasions of the inner part of the Gulf of Maine by tropical 

 planktonic animals do take place it is usually in the persons of but few individuals 

 and fewer species. 



How slightly this tropical pelagic community encroaches on Georges Bank even 

 in midsummer, when abundantly represented only 15 to 20 miles seaward from its 

 200-meter (100-fathom) contour, was brought forcibly to our attention in July, 

 1914, when only occasional warm-water animals or plants (e. g., Pterotrachea Icerau- 

 denii, Doliolum, Phronima, a phyllosome larva, and the tropical pteropod Cavolina 

 tridentata) occurred over the southern edge of the bank (station 10219) where the 

 plankton was otherwise boreal, in spite of the rich and varied tropical plankton 

 we have just mentioned (p. 54) as occupying the warmer water over the continental 

 slope only a few miles farther out. 



Tropical pelagic animals have been found even more rarely in the inner parts of 

 the Gulf of Maine than along the offshore banks, as might be expected. In fact, 

 the euphausiid shrimp Thysanoessa gregaria (p. 142) is the only member of this com- 

 munity occurring regularly there (but see, also, Sagitta serratodentata, discussed on 

 p. 320). Except for these, the complete list of tropical planktonic animals so far 

 detected in our catches in the gulf proper is brief. Among copepods the genera 

 Eucalanus, Dwightia, Eucheirella, Pleuromamma, and Rhincalanus may be so 

 classed, because all of them undoubtedly enter the gulf from the inner edge of the 

 Gulf Stream, and, judging from their rarity, are unable to establish themselves in 

 its cool waters, though properly speaking they are oceanic-Atlantic rather than 

 typically tropical. The status of each in the gulf is given in detail in the chapter 

 on copepods. The euphausiid shrimp Nematoscelis megalops, often plentiful along 

 the continental slope, appears only as a stray in the interior parts of the gulf (p. 146). 

 Salpa? (perhaps the best tropical indicators of all) have been taken at a number of 

 stations, usually represented, however, by few examples. 



This was the case with Salpa fusiformis near German Bank and off Lurcher 

 Shoal, August 14, 1912 (stations 10030 and 10031), though other scattered speci- 

 mens were seen floating on the run from one station to the other. A few Salpa tilesii 

 were also taken in the tow near Lurcher Shoal, August 12, 1913 (station 10096). 

 Huntsman (1921) records five S. fusiformis found on the beach at Campobello 

 Island (New Brunswick) in the autumn of 1913, and two S. zonaria taken in 

 that general region (probably near Grand Manan) in 1910. On September 30, 

 1912, Capt. John McFarland, of the fishing schooner Victor, to whom the Bureau 

 of Fisheries is indebted for other interesting tow-net hauls, made a large catch of 

 S. mucronata 25 miles off Chatham, Cape Cod; and fishermen reported great 



