306 bulletin: museum of comparative zoology. 



occasionally appear there both in summer (1914a) and in winter 

 (1914b). 



The demarcation between the ranges of Limaeina balea and of the 

 warm water pteropods and heteropods, i. e., the various species of 

 Creseis, Corolla, Limaeina inflata, Pterotrachea, Firoloida, and Atlanta, 

 was remarkably sharp, for the latter were only taken at the southern 

 and Gulf Stream stations where Limaeina balea was lacking (Fig. 72) ; 

 and not a specimen of any of them was found at any of the northern 

 stations where Limaeina balea occurred, except for a single Atlanta 

 off Gloucester. They are all oceanic, as pointed out by ]Meisenheimer 

 (1905). None of them occurred regularly, only one {Creseis conica) at 

 as many as five of the eighteen stations south of the limits of Limaeina 

 balea; and the total number of specimens of this species was only 

 forty-nine. The other warm water forms were even more sporadic in 

 their distribution : — Corolla calceola, Firoloida, and Creseis acicula oc- 

 curring at four stations each; the others at only one or two. Under 

 these circumstances it is impossible to say much about the influence 

 of hydrographic conditions on their distribution further than to point 

 out that all have a southern, or oceanic origin, and that it is doubtful 

 whether any of them would have been found in the coast water in 

 winter. Direct evidence to the effect that they are summer visitors 

 only is afforded by the fact that none of them were taken by Capt. 

 McFarland off Cape May in May, 1913, although several were en- 

 countered there in July. 



The occurrence of two living specimens of Diacria trispinosa, and 

 of an Atlanta, in a haul off Gloucester early in July is surprising, 

 because it is certain that neither of these genera is a regular inhabitant 

 of the Gulf of Maine; both belong to the warmer parts of the north 

 Atlantic, not to boreal w^aters (Meisenheimer, 1905). It is difficult to 

 account for their presence, because they were taken with an otherwise 

 typical boreal assemblage of plankton organisms, e. g., Calanus, Euthe- 

 misto.. 



Pelagic hydroids. 



by c. mclean eraser. 



During the month of July, 1913, the Grampus made a collection of 

 floating hydroids off George's Bank, which, through the kindness of 

 Dr. H. B. Bigelow, was sent to me for examination. Under ordinary 

 circumstances the material would scarcely be worth a comment as 



