PLANKTON OF THE GULF OF MAINE 



431 



c. 



July 9, 1913, station 10059 (fig. 123): 

 Diatoms very abundant. 

 *Guinardia flaccida dominant. 

 *Eucampia zodiacus dominant. 



*Biddulphia alternans. 

 *Coseinodiscus asteromphalus. 

 *Pleurosigma normanii. 

 *Rhizosolenia alata. 

 *R. shrubsolei. 

 *R. stolforthii. 

 *R. styliformis. 



Skeletonema costatum. 

 *Stephanopy.\is turris. 



D. July 23, 1916, station 10347 (fig. 121): 

 Diatoms very abundant. 

 ♦Thalassiothrix longissima doini 

 ♦Rhizosolenia styliformis dominant. 

 (Both together constitute 90 per rent 

 of the phytoplankton.) 



*Actinoptychus undulatus. 

 *Biddulphia alternans. 

 *Coseinodiseus concinnns 

 *C. oeulus-iridis. 

 *C. woodwardii. 

 *Pleurosigma normanii. 

 *Rhaphoneis amphiceros. 



13. — Shallow water south of Marthas Vineyard 



A. August 25, 1914, station 10258 (fig. 125): 

 Very abundant diatom plankton. 

 Rhizosolenia semispina 100 per cent 

 of a large sample. 



A. August 25, 1914— Continued. 

 Guinardia flaccida S. 

 No other diatoms noted. 



Notes on the dominant genera of diatoms 



On the following pages such notes are given on the status of the more prominent 

 genera as the preliminary examination of the tow nettings warrant. For convenient 

 reference the genera are arranged alphabetically. 



Asterlonella 



Asterionrtla japonica, as noted above (p. 392), occurred in extraordinary abundance 

 in August, 1912. During that summer we first found it close to land in Ipswich Bay 

 on July 8 (station 10008; it was not in Massachusetts Bay at that time), again in the 

 coastal zone between Cape Elizabeth and Penobscot Bay the next week (stations 

 10016 to 10021), and near Lurcher Shoal off Yarmouth, Nova Scotia, on August 15 

 (station 10031) ; likewise in the basin near Mount Desert Rock (station 10032) and off 

 the mouth of the Grand Manan Channel (station 10036) a few days later — captures so 

 widely separated that its range must then have included the whole northern coastal 

 belt of the gulf, though nowhere in any notable abundance. During the last half of 

 August it flowered in such abundance that on the 21st, when "passing Great Duck 

 Island, one of the small islands off Mount Desert, the appearance of the water was 

 noticeably soupy, and immediately the vessel was hove to and a surface haul made 

 with the No. 20 net. When brought on board, the net was filled with a brown slimy 

 mass, which on examination proved to consist almost wholly of countless numbers of 

 chains of Asteriondla japonica * * *" (Bigelow, 1914 p. 133). 



This swarm extended westward, though gradually diminishing in density, right 

 across the mouth of Penobscot Bay to the neighborhood of Seguin Island, where there 

 was such a sudden transition to clear water with very little phytoplankton that the 



61 Not examined by Doctor Mann. 

 75898—26 28 



