106 DEPARTMENT OF THE: NAVAL SERVICE 
7 GEORGE V, A. 1917 
Nitschia—Though represented generally, and by a large number of species, few 
of these are found in the-plankton. The most common are N. sigmoidea and N. 
closterium, found near St. Andrews, April 19. N. Sigma was observed at the same — 
station July 7th, and NV. seriata in August. Besides the above NV. dubia and N. vermi- 
cularis were found at St. Martins in August; N. closterium, N. sigmoidea and N. 
vermicularis in St. John harbour during the same month. WN. seriata was obtained 
from the “ Prince” collection, at Station 3 (between Head harbour and the Wolves) 
September 18; but not from other points. None were observed in October gather- 
ings. 
Pleurosigma.—Though a littoral and brackish water genus, some of its species 
are also pelagic and planktonic. P. decorum and P. formosum were found in St. 
Andrews harbour February 19; P. fasciola and P. decorum at the Biological Station 
February 27; the same at the Reversing Falls. St. John, February 14; at Doucette’s 
island in March; P. intermedium and others in St. Andrews harbour, April 17; P. 
fasciola at West Quoddy June 17; P. Balticum and P. fasciola at the Biological 
Station June 28; and P. obscurum at St. Martins in August. P. fasciola and P. 
formosum were found in L’Etang harbour August 10, and P. Balticum at Tyne- 
mouth creek August. No representatives of the genus were found in the “ Prince” 
colleetions of September or October. 
Rhabdonema.—Isolated frustules, and more rarely short chains of R. arcuatum 
are occasionally met with in the plankton, but are not common. 
Rhizosolenia.—This is one of the typically planktonic genera, and as represented 
by R. setigera, is often very abundant. It was obtained as early as January 16 at 
Wilson’s beach, Campbello, and at Seeley’s cove January 31; in St. Andrews 
harbour February 19, and the Biological Station February 27; at Joe’s Point, St. 
Andrews, and the St. Croix river March 28; and at Robbinstown May 23; but 
appears to be absent in June and July. It was found at Campbello August 1, and 
L’Etang harbour August 10, also at Tynemouth creek the same month. In the 
“Prince” series it was September 27 at the lower end of Annapolis Basin (with 
spear-like enlargements of the terminal spines, not yet observed in the bay of Fundy), 
and on the Annapolis river, near Goat island. In the same series it occurs as found 
in St. Andrews harbour October 10, St. John harbour October 19 and Grand Manan 
(abundantly). 
Skeletonema.—This is another of the distinctly planktonic genera, its adaptation 
to a floating life being effected by the association of the frustules in long chains, some- 
times embracing forty or fifty individuals. It is, however, characterized by much 
diversity as regards size, distribution and seasonal variations. It was found at Bald 
Head January 15, St. Andrews harbour February 19 and Manawagonish, St. John 
county Febraury 5; but no occurrences have been recorded at any station for March, 
April, May, or June. It was found at Eastport July 29, Campbello August 1 (zare). 
L’Etang harbour and Deadman’s harbour August 10. From the “ Prince” collections, 
in September and October, it appears to be wholly absent. + 
Thalassiosira-—Another characteristic plankton genus, easily recognized by the 
interposition between the widely separated frustules of long filamentous threads (Slime 
threads of the Germans). Of its two species Th. Nordenskioldu is the more common, 
but exhibits great seasonal differences. It was found in January and February at the 
Biological Station, again very abundantly about Joe’s point, St. Andrews, on May 27, 
as also at La Tete, Campbello and Eastport; and at the latter station again on July 
29: Biological Station March 17, St. Croix river and La Tete March 28; Doucette’s 
island March 27; Joe’s point April 30, St. Andrews harbour April 18, very abundantly; 
