360 Wisconsin Academy of Sciences, Arts , and Letters. 
since there is a ring of small conical verrncae on the apex of each 
semicell, the number of verrucae corresponding to the number of 
rays. The majority of the cells collected are five-armed. A cur¬ 
ious malformation of a semicell is shown in figure 11. 
The alga was forming zygospores in the plankton of Lake 
Joseph. This discovery of zygospores in the plankton is most 
unusual, and only two cases are on record of zygospore formation 
by a plankton Desmid. 
forma tetragona forma nova. PI. XIII, fig. 12. 
Semicells with four processes, spread of processes greater than 
in the typical five- or six-rayed variety. 
Breadth (without processes) 20-22.5 n; (with processes) 93- 
105 /x. 
St. Mary (rr). 
Four-rayed cells were found in St. Mary’s Lake but not noted 
among the thousands of cells collected from other lakes. 
Staurastrum leptocanthum Nords. 
Black (1) (aaa), Burned Hock (rrr), Butterfly (s), Clear (rrr), Echo 
(rr), Gull (1) (c), Gull (2) (r), Joseph (rrr), Little Dudley (rrr), Long 
(2) (r), McGowan (r), Muldrew (rrr), iNelson (s), Otter (rrr), Pennsyl¬ 
vania (rr), Pine (rrr), Rosseau (rrr), Rowley (rrr), Silver (1) (ss), 
Strange (rr). 
Staurastrum Arctiscon (Ehr.) Lund. 
Basil (rrr), Big Dudley (rrr), Burned Rock (rr), Clear (2) (rrr), Lit¬ 
tle Dudley (sss), Long (1) (rrr), Loon (rrr), Nelson (rrr), Otter (rrr), 
Strange (rrr). 
var. GLABRUM W. & G. S. West 
Rowley (rrr). 
Staurastrum tohopekaligense Wolle 
Loon (rrr). 
var. trifurcata W. & G. S. West 
Gull (1) (rr), Muskoka (rrr), Rowley (rr), Silver (1) (rr), Strange 
(rrr). 
COSMOCLADIUM Brebisson 1856 
Cosmocladium saxonium DeBary 
Marion (rrr), Rosseau (rrr), Rowley (rr). 
