30 
TRANSACTIONS AND PROCEEDINGS OF THE [ Szss. LXIX. 
S.—Plankton of Lochs Asta and Brindister, and also of Loch 
Beosetter, Bressay. 
This interesting species was first found by Wille in Norway, 
both in ordinary collections and in the plankton. It only differs. 
from O©. rectangularis (Nag.), Gay, in the irregularity of its. 
colonies, and in the total absence of pyrenoids. 
Schmidle has recently placed this Alga under a new genus— 
Willea, but a comparison of the colonies with those of C. 
rectangularis does not support this view. All the cells in a 
large colony of the latter species do not possess pyrenoids, and 
the only distinction of importance between these two species is the 
irregularity of the cell-division in Wille’s species. 
Genus SCENEDESMUS, Meyen. 
. bijugatus (Turp.), Kiitz. O.—W. of Kirkwall; Hoy. S.—Near 
Lerwick ; Scalloway ; Bressay. Plankton of Loch Asta. 
. obliquus (Turp.), Kitz. O.—Kirkwall. S8.—Near Lerwick. 
. quadricauda (Turp.), Bréb. O,—Kirkwall; Finstown. Plank- 
ton of Loch Kirbister. S.—Lerwick ; Neugles Water. Plankton 
of Lochs Asta and Clickhimin. Bressay, in ditches and in the 
plankton of Loch Beosetter. 
Var. abundans, Kirchn. S.—Bressay. Plankton of Loch Asta. 
. denticulatus, Lagerh. O.—W. of Kirkwall; near Finstown. 
S.—Near Lerwick ; Bressay. Plankton of Loch Asta. 
. acutiformis, Schroder, in “ Forschungsber. Biol. Stat. Plon,” v.,. 
1897, p.17, t. 2, £.4 
Var. Brasiliensis, nob. [S. brasiliensis, Bohlin, in “ Bihang till 
K. Sv. Vet.-Akad. Handl.,” Bd. 23, No. 7, 1897, p. 22, t. 1, 
f. 26-27; S. acutiformis, Schréd., var. spinuliferum, W. and 
G. S. West, “ Freshw. Alg. Koh Chang,” “ Botanick Tidsskrift,” 
Bd. 24, 1901, p. 98, t. 4, f. 46-49.] 
Long. cell. sine spin. 20-27; lat. cell. 5-8»; long. spin. 
1°5-3°8y (figs. 8 and 9). 
S.—Plankton of Loch Asta. 
This variety undoubtedly combines the characters of S. 
denticulatus, Lagerh. ; and S. acutiformis, Schroder, and could 
be placed equally well as a variety of either species. 
Genus ANKISTRODESMUS, Corda. 
. faleatus (Corda), Ralfs. [Rhaphidiwm fasciculatum, Kiitz ; Rh.. 
polymorphum, Fresen., var. faleatum, Rabenh.] O.—Finstown. 
S.—Near Lerwick; near Scalloway. Plankton of Neugles 
Water, and also of Loch Beosetter, Bressay. 
Var. acicularis (A. Br.), G.S. West. [Rhaphidiwm aciculare, 
A. Br.; Rh. polymorphum, Fresen, var. aciculare, Rabenh.] 
O.—Kirkwall. Plankton of Loch Kirbister. S.—Near Lerwick ; 
near Scalloway ; Neugles Water. Plankton of Loch Clickhimin. 
Var. mirabilis, G. S. West. [Rh. polymorphum, Fresen, var. 
mirabile, W. and G. S. West.]  S.—Near Scalloway. Plankton 
of Lochs Sandy and Trebister, and also of Loch Beosetter,. 
Bressay. 
Var. spiralis (Turn.), G.S. West. [Rh. spirale, Turn.] S.— 
Plankton of Loch Asta. : 
274. A. Pfitzeri (Schroder), G. 8. West. [Rh. Pfitzert, Schroder.] S.— 
Plankton of Loch Asta, and of Loch Beosetter, Bressay. 
