Smith—Phytoplankton of the Muskoka Region . 
333 
WE ST ELLA de Wildeman 1897 
Westell a botryoides (W. West) de Wild. 
Butterfly (rrr), Mud (rrr), Muskoka (rrr), Portage (rrr), Round (1) 
(rrr), Vernon (rr). 
Family AUTOSPORACEAE 
OOCYSTIS Nageli 1845 
Oocystis Borgei Snow 
Butterfly (rrr), Otter (r), Rowley (ss). 
Oocystis parya W. & G. S. West 
Black (1) (rrr), Leech (rrr). 
Oocystis lacustris Chodat 
Loon (rrr). 
TETRAEDRON Kiitzing 1845 
Tetraedron trigonum (Nag.) Hansg. 
Black (1) (rr), Burned Rock (rrr), Butterfly (rr), Cornell (rrr), 
Harbon (rr), Marion (rrr), Otter (rr), Pennsylvania (rrr), Pine (rrr), 
Rowley (rrr), Silver (1), (rrr), White (rrr). 
var. gracile (Reinsch) de Toni 
Butterfly (rrr). 
Tetraedron minimum (A. Br.) Hansg. 
Black (1) (rrr), Butterfly (rrr), Clear (2) (rrr), Harbon (rrr). 
Tetraedron qnadrilobatmn sp. nov. PL VIII, figs. 14-18. 
Cells small, flattened, four-cornered, generally with all four 
corners in the same plane, sometimes with halves of cell cruciate. 
Sides of cells deeply emarginate and giving the cells a cruciform 
appearance. Angles broadly rounded, smooth, without spines. 
Side view of flattened cells broadly ellipsoid. Chloroplast single, 
parietal, without a pyrenoid. 
Diameter of cells 7.5-17 thickness of cells 4-6 /a. 
Clear (2) (rrr). Corner (rrr), Lake of Bays (rrr), Vernon (rr). 
This species is about the size of the familiar T. minimum (A. 
Br.) Hansg., but the sides are more deeply emarginate and the 
