546 MR. W. WEST AND PROF. G. S. WEST ON 
form and var. bidentatum nob. ( = Staurastrum bidentatum, 
Wittr.). 
23. STAURASTRUM BRASILIENSE, NWordst. in Vidensk. Meddel. 
(1870) p. 227, t. 4. f. 39. 
Var. Lunpetuit, West & G. S. West, in Trans. Linn. Soc., 
ser. 2, Bot. v. (1896) p. 259; Journ. Bot. xxxviii. (1900) p. 295. 
—S. brasiliense, var. Lundellianum, Schmidle, in Bih. till K. 
Sv. Vet.-Akad. Handl. Bd. xxiv. (1898) Atd. 111. no. 8, p. 58. 
Long. sine spin. 79, cum spin. 125; lat. sine spin. 68 p, 
cum spin. 125 pw; lat. isthm. 30 p. 
Hab. Loch a Gharbh Bhaid Mhoir, Sutherland. Loch Nan 
Eun, N. Uist, Outer Hebrides. 
All the specimens observed were pentagonal in vertical view, 
and were precisely like numerous examples seen from Wales 
and the West of Ireland. It appears to be a Desmid of a dis- 
tinctly western type, and even in those areas in which it occurs 
it is more abundant in the plankton than in bog-pools. 
24, S. BREvVIsPINUM, Bréb. in Ralfs, Brit. Desm. 1848, p. 124, 
t. 34. f. 7. 
Var. RetUSUM, Borge, in Bih. till K. Sv. Vet.-Akad. Hand. 
Bd. xix. (1894) no. 5, p. 36, t. 3. f. 42. 
Long. 52; lat. 41 p; lat. isthm. 13:5 p. (Pl. 14. fig. 6.) 
Hab. Loch Nan Cuinue, Sutherland (J. Murray) ! 
25. 8. tuNatUM, Ralfs, Brit. Desm. 1848, p. 124, t. 34. f. 12. 
Var. PLANCTONICUM, var.n. (PI. 16. figs. 11, 12.) 
Var. paullo major et latior, angulis semicellularum acutioribus, 
spinis minoribus; semicellula a vertice vis cum lateribus 
latissinse recusis. 
Long. 40-44 4; lat. sine spin. 42-50; long. spin. 3-5°5 p; 
lat. isthm. 14°5-16 p. 
Hab. Loch Shin and Loch a Gharbh Bhaid Mhoir, Sutherland. 
Tioch Mor Bharabhais, Lewis; and Loch Nan Eun, N. Uist, 
Outer Hebrides. Loch Doon, Ayrshire. Loch Tay, Perthshire. 
This variety is one of the most frequent Desmids of the 
Scottish plankton, and is distinguished from the type by the 
more angular semicells in which the angles are more produced, 
and by the smaller spines at the angles. There is no very 
obvious constriction at the base of the spines. The entire cell is 
finely granulated, the granules being very acute and arranged in 
concentric rings round the angles. 
7. 
