24 
TRANSACTIONS AND PROCEEDINGS OF THE [ Szss. LXIX. 
190. A. triangularis, Lagerh., in “ Ofvers. af K. Vet.-Akad. Forh.,” 1885, 
iSite 
192. 
193. 
194. 
195. 
196. 
197. 
as 
Ss 
. cuspidatum, Bréb. O.—Finstown. S 
no. 7, p. 244, t. 27, f. 22. [A. Incus, var. triangularis, Lagerh., 
in “ Nuova Notarisia,”’ iv., 1893, p. 182.] 
Long. 25-264; lat. sine spin. 20-244 ; cum. spin. 61-65°5y ; 
lat. isthm. 5°2—6u ; crass. 10°5-I1p. 
S.—Both at the margins, and in the plankton of Loch 
Beosetter, Bressay. 
The specimens were not quite typical in form, the apices of the 
semi-cells being straight or very slightly concave, thus resembling 
the var. Americanum. 
Var. subtriangularis (Borge), Nob. [A. Incus, var. subtri- 
angularts, Borge, in “ Botaniska Notiser,” 1897, p. 212, t. 3, 
f. 4; A. triangularis, var. hebridarum, W. and G. 8. West, 
in “Journ. Linn. Soe.,” bot. xxxv., 1903, p. 542.] 
Long. 30-31'5u; lat. sine spin. 23-254 ; cum spin. 75-78p ; 
lat. isthm. 8u (fig. 36). 
S.—Plankton of Loch Beosetter, Bressay. 
The outline of this variety has been well figured by Borge, but 
he did not mention the scattered scrobiculations on the cell-wall. 
It is general in the plankton of the lakes in the West of Scotland 
and the Outer Hebrides. 
Genus STAURASTRUM, Meyen. 
dejectum, Bréb. O.—Kirkwall; Finstown. S,—Bressay. 
Plankton of Lochs Asta and Brindister, and also of Neugles 
Water. 
Var. inflatum, West. S.—Plankton of Neugles Water, Lochs 
Asta and Brindister, and also of Loch Beosetter, Bressay. 
. Dickiei, Ralfs. S.—Loch Brindister. 
. glabrum (Ehrenb.), Ralfs. S.—Near Lerwick. 
. curvatum, West. S.—Plankton of Loch Asta. 
. jaculiferum, West. O.—Plankton of Loch Kirbister. S.— 
Plankton of Neugles Water and Loch Trebister. 
. brevispinum, Bréb. S.—Plankton of Loch Clickhimin, and of 
Loch Beosetter, Bressay. 
Some forms of this species were noticed in the plankton of 
Loch Asta. They differed somewhat from more typical forms in 
the relative position of the mucros (fig. 32). 
Lerwick. 
Var. maximum, West. S.—Plankton of Neugles Water, Lochs 
Asta, Brindister, and Sandy. Bressay, both in ditches and in 
the plankton of Loch Beosetter. 
. OMeariz, Arch. O.—Hoy. 
. lunatum, Ralfs, var. planctonicum, W. and G. S. West. S.— 
ae 
Plankton of Loch Brindister, and also of Loch Beosetter, Bressay. 
pelagicum, W. and G. 8S. West. S.—Plankton of Loch Asta, and 
also of Loch Beosetter, Bressay. 
Avicula, Bréb., var. subarcuatum (Wolle), West. 0.—Kirkwall ; 
Finstown. S§.—Scalloway ; Bressay. 
granulosum (Ehrenb.), “ Ralfs, Brit. Desm.,” 1848, p. 217 ; W. and 
G. S. West, in “ Trans. Roy. Irish Acad.,” xxxii., 1902, p. 45, t. 2, 
£94. 
[Desnudium granulosum, Ehrenb., 1839. Phycastrum granu- 
losum, Kiitz, “Spec. Algar.,” 1849, p. 180. Staurastrum lunatum, 
Ralfs, var. subarmatum, West, in “Journ. Roy. Micr. Soc.,” 
1894, p. 10, t. 2, £. 47.] 
