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. 
*Coscinodiscus asteromphalus. 
*Pleurosigma normanii. 
*Rhizosolenia alata. 
*R. shrubsolei. 
*R. stolforthii. 
*R. styliformis. 
Skeletonema costatum. 
*Stephanopyxis turris. 
13. — Shallow water sout 
A. August 25, 1914, station 10258 (fig. 125) : 
Very abundant diatom plankton. 
Rhizosolenia semispina 100 per cent 
of a large sample. 
D. July 23, 1916, station 10347 (fig. 124) : 
Diatoms very abundant. 
*Thalassiothrix longissima dominant. 
*Rhizosolenia styliformis dominant. 
(Both together constitute 90 per cent 
of the phytoplankton.) 
*Actinoptychus undulatus. 
*Biddulphia alternans. 
*Coscinodiscus concinnus 
*C. oculus-iridis. 
*C. woodwardii. 
*Pleurosigma normanii. 
*Rhaphoneis amphiceros. 
of Marthas Vineyard 61 
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. 
Asterionella 
Asterionella 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 wdth a brown slimy 
mass, which on examination proved to consist almost wholly of countless numbers of 
chains oi Asterionella 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 
•* Not examined by Doctor Mann. 
