BIGELOW: EXPLORATIONS OF THE COAST WATERS. 305 



cruises in the Gulf Phialidiuni was found swarming, but each time 

 in a different phice; near Mt. Desert Rock and off the Kennebec 

 river in 1912; off Penobscot Bay in 1913; over the Eastern Basin 

 (Station 10249) in 1914; and in Kittery River, and off Rye in 1915. 

 Our experience has always been that Phialidium is most numerous 

 at or near the surface; and this is well illustrated at Station 10249, 

 where only a few were taken in the 50 meter, none in the 175 meter 

 haul, though it was very numerous on the surface. As yet it has 

 not been found on Georges Bank on the one hand, nor off the south 

 coast of Xova Scotia on the other; and it is probable that the Gulf 

 of Maine is the northern limit to its abundance. The earliest records 

 for Phialidium are in July and it is usually most numerous during 

 August. 



The comparative abundance of Mitrocoma cruciata in May and June 

 1915, and its absence during summer and autumn, explains its rarity 

 during the July and August cruises of previous years (p. 304; 1915, 

 p. 316). This agrees with Alexander Agassiz's statement that it is 

 frequently found in Massachusetts Bay during early summer (1865, 

 p. 102). As the table shows, its period of abundance hardly overlaps 

 that of Phialidium. 



StauropJiora viertensii has been found, in past years, in most parts 

 of the Gulf, (1914a, 1915). ' But so far as the hauls can be trusted, 

 there has been a steady decrease in its numbers since 1912. Thus 

 Staurophora was taken at many stations in that year, often in swarms : 

 at seven stations, usually in small numbers, in 1913: in 1914 it was 

 found at three stations, only once (Station 10214) in any numbers, 

 although the work was done at about the same time of year; and in 

 1915, it was taken at four stations, a total of only four specimens. 

 Staurophora has not been taken on Georges Bank, nor south of 

 Cape Cod: but it is recorded from Woods Hole (Hargitt, 1905). 



The other neritic Medusae occur so rarely and irregularly in the 

 hauls that I need only note that the Obelia on the northern part of 

 Georges Bank were no doubt associated with the Obelia hydroids 

 found floating there (p. 252, 1915). 



Only one oceanic Medusa, Aglantha digitate, occurs with any 

 regularity in our waters; and enough records for this species have now 

 been accumulated to show that it may be expected anywhere in the 

 Gulf; though never abundant there. It is also taken in hauls in 

 the zone of mixed water over the continental slope, often in some 

 numbers (1915); but so far has not been recorded from undiluted 

 Gulf Stream water {c. g. it occurred at Stations 10220 and 10233, but 

 not at 10218). 



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