al “Oe 
t 
= 
_— 
tes 
SCOTTISH FRESHWATER PLANKTON. 55) 
Some very large forms were observed from Loch Shin, Suther- 
land; they were both 5- and 6-rayed, and reached a diameter 
(with processes) of 122 p. 
Var. SUPERNUMERARIUM, var. n. (PI. 18. fig. 8.) 
Var. semicellulis cum processu parvo supernumerario inter 
processibus superioribus inferioribusque. 
Long. sine proc. 51 y, cum proce. 65 yw; lat. sine proc. cire. 42- 
46 p, cum proc. 84°5-90 uw; lat. isthm. 12 p. 
Hab. Loch Shin, Sutherland. 
35. Stavrasrrum Arctiscon, Lund. in Nov. Act. R. Soc. 
Scient. Upsala, ser. 3, viii. (1871) p. 7¢, t. 4. f. 8—Xanthidium 
Arctiscon, Ehrenb. 
Long. sine proce. 67-77 p, cum proc. 105-126 p; lat. sine proc. 
42-49 uw, cum proc. 94-121 pv; Jat. isthm. 24-26 p. 
Hab. Loch Shin, Sutherland. Loch Laxadale, Harris; and 
Loch Nan Eun, N. Uist, Outer Hebrides. Loch Doon, Ayr- 
shire. 
This is another Desmid of a distinctly western type, and it is 
much more abundant in the plankton than in any other habitat 
in the areas in which it is found. 
The processes vary considerably in length, and there may be 
from two to seven rings of small denticulations on each process. 
36. S. aneuLatum, West, ‘ Desm. Massachusetts, Journ. 
Roy. Mier. Soc. (1888) p. 20, t. 3. f. 20. 
Var. PLANCTONICUM, var.n. (PI. 16. fig. 10.) 
Var. minor, semicellulis rhomboideo-depressis, angulis apiculo 
minuto instructis. 
Long. 47 4; lat. 44-46 p ; lat. isthm. 9°5-10°5 p. 
Hab. Loch Shin, Sutherland. 
Genus SponpyLosium, Bréb. 
37. S. putcHRuM, Arch. in Pritch. Infus. ed. 4, 1861, p. 724.— 
Spherozosma pulehrum, Bail. in Ralfs, Brit. Desm. 1848, 
p- 209, t. 35. f. 2. 
Var. PLANUM.—Spherozosma pulchrum, Bail., var. planum, 
Wolle, Desm. U.S. 1884, p- 29, t. 4. ff. 3, 4. 
Small forms :—Long. 16°5-19°5 p: lat. 18-25 p; lat. isthm. 
S-LL‘5 pe 
