284 bulletin: museum of comparative zoology. 



Brown's Bank, the coastal water south of Nova Scotia, the Woods 

 Hole region, and over the continental shelf south of Marthas ^'ineyard ; 

 but not from the continental slope. His failure to find it in the large 

 collections from outside the 100 fathom curve off Marthas Vineyard 

 can hardly be accidental, as hosts of other euphausiids have been 

 taken there on many occasions. In short, T. inermis is a charac- 

 teristic inhabitant of ^ the cold coastal water from southern Nova 

 Scotia, as far west as Long Island. But it is evidently not at home 

 in the high temperatures outside the continental slope, though of 

 course it may be accidentally swept out into the Gulf Stream by the 

 mixture of the two waters which takefe place there. Its rarity or 

 absence off Halifax in 1914 reflects the local rarity of the group and 

 poverty of the macroplankton as a whole (p. 309). 



Thysanoessa longicaudafa, likewise a boreal species (Kramp, 1913, 

 Zimmer, 1909) is as generally distributed in the Gulf as T. inermis. 

 But it occurred less regularly, and at fewer stations in 1912, 1914, 

 and especially in 1915 (when it was detected only once. Station 10304). 

 On the other hand, it was taken at three deep stations over the slope, 

 though not at the one (Station 10218) where salinity and temperature 

 were most characteristically oceanic, and Hansen (1915) likewise 

 records it from many stations over the continental slope, and the edge 

 of the Gulf Stream south of Marthas Vineyard. Apparently it is 

 less definitely associated with the coast water than is T. inermis. 



Thysanoessa raschii, likewise a northern form (Kramp, 1913, 

 Zimmer, 1909), is much less common in our waters in summer than 

 either of the preceding species, for it was not represented at all in 

 the hauls in July 1912; appeared at only five stations in 1914 (two 

 in the Gulf, two in the cold water off southern Nova Scotia, Stations 

 10231, 10232, one off Marthas Vineyard, Station 10259); and at 

 three Stations (10277, 10318, 10329)* in 1915. But it swarmed in 

 the western part of the Gulf during the early spring of 1913 (1914b). 

 Hansen's (1915) records are chiefly from the Gulf of St. Lawrence. 

 But they include one station on Brown's Bank, August 1877, and one 

 off the northern end of Cape Cod, August 1881. Apparently the Gulf 

 of Maine is the extreme southern limit for this species in summer. 



The occurrence of Thysanoessa gregaria, side by side with T. inermis 

 and T. raschii is, as Dr. Tattersall writes me, an interesting pheno- 

 menon, because, unlike them, it is a typical subtropical form (Zimmer, 

 1909), its presence, like that of Salpa, and other tropical animals, 

 indicating the presence of southern, i. e., ocean, waters in the Gulf 

 (p. 239). Thysanoessa gregaria is much less common in the Gulf 



