416 MR. G. S. WEST ON VARIATION IN THE DESMIDIER. 
Figs. 9-16. Micrasterias truncata, Bréb. x220. 9, specimen from Widdale 
Beck, N. Yorks.; 10, from near Clapham, W. Yorks.; 11, from 
Bowness, Westmoreland ; 12, from Glen Shee, Perthshire, Scotland ; 
13, from Llyn Padarn, N. Wales; 14, from Capel Curig, N. Wales; 
15, from Thursley Common, Surrey; 16, from Minneapolis, 
Minnesota, U.S.A. 
, PLATE 10. 
Figs. 1-6. Cosmarium leve, Rabenh. x520. 1 & 2, specimens from near 
Paris; 3-6, from Hanka Deela, Somaliland. 
» 4-9. Cosmarium leve, Rabenh., var. septentrionale, Wille. x520. 7, 
specimen from Cocket Moss, near Giggleswick, W. Yorks.; 8, from 
Epping Forest, Essex ; 9, from Borrowdale, Cumberland. 
» 10-21. Cosmarium Regnesii, Reinsch, and many forms intermediate 
between the type and var. montanum, Schmidle. 1280. 10-17, 
specimens from Puttenham Common, Surrey ; 13-17, showing pecu- 
liarities in division of cells; 18 (very large form) and 19, from Riecal] 
Common, E. Yorks.; 20 and 21 (very large form) from Pilmoor, 
near Thirsk, N. Yorks. 
» 22-28. Cosmarium biretum, Bréb. X520. All the specimens from the lake, 
Welsh Harp, Middlesex. 
» 29-84. Cosmarium biretum, Bréb., var trigibberum, Nordst. x 520. 29-31, 
and 34, specimens from The Washes, Sutton, Cambridgeshire; 32, 
from Whiteley Common, Surrey ; 33, from Roundhay Park, Leeds, 
W. Yorks. 
‘4, 90-90. Staurastrum furcigerum, Bréb,, one semicell typical and the other 
with six superior processes (as in forma eustephana, Nordst.). x 520. 
35, specimen from Birkhouse Moor Tarn, Helvellyn, Westmoreland ; 
36, from Pilmoor, near Thirsk, N. Yorks. 
Pare 11. 
Figs. 1-4. Cosmarium orthostichum, Lund. 520. 1, specimen from Thursley 
Common, Surrey; 2, from Ballynahinch, Connemara, Ireland; 3, 
from the United States; 4, from the New Forest, Hants. 
» 5-15. Staurastrum brachiatum, Ralfs. x520. 5-8, specimens from near 
Devil’s Jumps, Frensham, Surrey; 9, from Slieve Donard, Mourne 
Mts, Co, Antrim, Ireland; 10, from Orono, Maine, USA ; 11, 
from Puttenham Common, Surrey; 12, from Thursley Common, 
Surrey ; 13-15, from Penzance, Cornwall. 
„ 16-20. Staurastrum Reinschii, Roy. x520. 16 & 17, specimens from 
near Devil's Jumps, Frensham, Surrey (175" is slightly oblique); 
18 & 19, from Lund’s Fell, N. Yorks. (194'is oblique); 20, from 
Roughton Moor, Cornwall. 
» 21-27. Staurastrum crenulatum, Delp. X520. All specimens from 
Roundhay Park, Leeds, W. Yorks. 
» 28-32. Staurastrum aculeatum, Menegh. X520. 28 & 29, specimens 
from Orono, Maine, U.S.A. ; 30, from Thursley Common, Surrey ; 31, 
from Capel Curig, N. Wales; 32, from Minneapolis, Minnesota, U.S.A, 
