350 BULLETIN OP THE BUREAU OF FISHERIES 



that Mitrocoma, like Phialidium, probably passes through its hydroid stage over 

 rather a wide range of depth and perhaps down to 100 meters or more. 



Up to the present time all known captures of M. cruciata have been from the 

 Gulf of Maine except for a few taken off Shelburne, Nova Scotia, by the Grampus 

 on June 23, 1915 (stations 10291 and 10293), and it seems nowhere to be abundant 

 even in the gulf, for our tow nets have never yielded more than a dozen specimens 

 or so at any one station. 



Phialidium languidum' (A. Agassiz) 



Phialidium languidum (fig. 98) is the only one of the smaller medusae with 

 hydroid stage that is ever an important factor in the plankton in the open basin 

 of the Gulf of Maine. 91 



The young medusas of Phialidium appear in the waters of Massachusetts Bay 

 late in May (A. Agassiz, 1865, fig. 96), and to judge from Mayer's (1910) observa- 

 tions at Newport it is probable that they are constantly set free from their hydroid 

 stocks from that time until July, but they are so small and so easily destroyed in 

 their earliest stages that it is not until they have reached almost mature size that 

 we have recognized them in the general mass of plankton taken by our tow nets. 

 The adults are most numerous from the last week of July through August, to vanish 

 from Massachusetts Bay by the end of September, and our latest autumnal records 

 of Phialidium are for October 9 in the coastal zone between Grand Manan and 

 Penobscot Bay in 1915 (for list of stations see Bigelow, 1917, p. 304). The abun- 

 dance in which these medusas sometimes occur was mentioned by Alexander Agassiz 

 (1865, p. 73), who found them "in immense shoals on warm, sunny, still days" in 

 Massachusetts Bay during September. Mayer (1910), too, observes that from July 

 until September they are extremely abundant along the New England coast, par- 

 ticularly at Eastport, where they crowd the water of the harbor, and my own more 

 recent experience has been similar. For instance, we found Phialidium common 

 in every harbor and bay that we entered during the month of August in 1912, espe- 

 cially so in Gloucester Harbor, at the mouth of the Piscataqua River, at Boothbay, 

 and at Eastport. I had previously seen this medusa in myriads both at Grand 

 Manan during August, 1910 (whence Fewkes (1888) also records it), and along the 

 southern shores of Massachusetts Bay. The Grampus likewise found it swarming 

 near Mount Desert Rock on August 16, 1912 (station 10032), and near Seguin 

 Island off the mouth of the Kennebec River on the 22d of that month (station 

 10040) ; even as far offshore as the eastern basin on August 13, 1914 (station 10249). 

 and also in the Piscataqua River and off Rye, N. H., on July 23. 1915. 



We have no record of Phialidium out in the open gulf prior to the first of 

 August, either because the young medusas are confined to the immediate vicinity of 

 their shallow nurseries along the coast or because they have not been recognized in 

 the tow, but during that month it occurs very generally right across the gulf north 

 of a line from Cape Cod to Cape Sable. 92 



60 For description and figures see A. Agassiz, 1865, p. 71; Mayer, 1910, p. 269. 



81 Other species are plentiful locally on Georges Bant. 



" For locality records, summers of 1912 to 1915, see Bigelow, 1914, p. 125 1915 p. 273 and 1917 pp. 303 and 304. 



