Smith—Phytoplankton of the Muskoka Region. 
359 
body of the semicell is also narrower than in S. Ophiura. The 
shape of the semicells and the sharp incurving of the rays are as 
Wolle describes them for S. ankyroides, but I find the ventral 
sides of the semicells straight instead of slightly undulate as he 
figures. S. ankyroides should be compared with S. pentacerum 
var. tetracerum (Wolle) ($. Ophiura var. tetracerum Wolle), 
from which it differs in the cell shape, heavier apical verrucae, 
lateral spines on rays and incurving of the rays. 
Staurastrum Arachne Ralfs, 
Big Dudley (rrr), Black (1) (rrr), Brush (sss), Harbon (rrr). 
var. curvatum W. & G. S. West 
Black (2) (r), Corner (rrr), Echo (sss), Henshaw (s), Otter (r) Pine 
(rr), Silver (2) (sss). 
Staurastrum Ophiura Lund. 
Brush (rrr), Burned Rock (rr"). Clear (1) (rrr), Clear (2) (rrr), 
Long (1) (rrr), Muldrew (rrr). 
Staurastrum rotula Nords. 
Henshaw (rr). 
Staurastrum limneticum var. burmense W. & G. S West. PL 
XIII, figs. 6-11. 
Cells five- or six-radiate. 
Zygospores spherical, furnished with long, slender, gradually 
tapering spines that are bifurcate at the apex, the bifurcate apical 
portion being recurved. 
Length cells (without processes) 35-44 /x, (with processes) 47- 
55 /a; breadth (without processes) 20-22.5 /x, (with processes) 
75-87.5 fi; breadth isthmus 8.5 /x. 
Diameter zygospore (without spines) 42-44 fi; (with spines) 
85-92 /x; length spines 20-24 /x. 
Black (1) (rrr), Black (2) (s), Brush (rrr), Burned Rock (r), Butterfly 
(ss), Clear (1) (rrr), Echo (r), Harbon (rrr), Gull (2) (ss), Joseph (ss). 
Loon (c), Muldrew (ss), Muskoka (ss), Nelson (s). Otter (r), Portage 
(rrr), Rosseau (r), Rowley (r), Round (2) (r), Silver (1) (rrr), Strange 
(rr), Vernon (ss). 
S. limneticum var. burmense has been collected from but one 
lake in Wisconsin, but is widely distributed in the portion of On¬ 
tario where these investigations were carried out. The Ontario 
specimens differ slightly from those the Wests found in Burma 
