This form differs from the typical by its broad, bilobed processes 

 and by the lateral walls of the cell being much less concave or 

 emarginate. It differs from var. polyfurcatum G. M. Smith in the 

 form and number of processes. 



Planktonic in lakes; also found in Manitowish River, Wisconsin. 



Tetraedron lobulatum var. polyfurcatum G. M.Smith 1916, p. 480 



PI. 60, Fig. 11 



Cells tetragonal, pyramidal or flattened, the angles extended into 

 processes which are dichotomously divided 3 to 5 times, the lobules 

 ending in 2 or 3 minute spines; margin of the cell concave between 

 the processes; cells 15-25/i, in diameter without processes, 35-70/i, in 

 diameter including processes. 



Rare; in the plankton of many lakes. Wis. 



Tetraedron lunula (Reinsch) Wille 1911, p. 60 

 PI. 60, Figs. 9, 10 

 Cells lunate, tapering to sharply pointed poles; the outer margin 

 more sharply curved than the inner, which is concave; cells ll-12;w 

 in diameter, 25-30/x long. 

 Plankter, in a small inlet of the Wisconsin River, Wisconsin. 



Tetraedron minimum (A. Braun) Hansgirg 1888a, p. 131 



PI. 60, Figs. 12-15 



Cells small, flat, tetragonal, the angles rounded and without spines 

 or processes, lobes sometimes cruciately arranged; margins of the 

 cell concave, with one frequently incised; cells (6)-14.5-20/x in 

 diameter. 



Common in the tychoplankton and euplankton of many lakes and 

 ponds. Mich., Wis. 



Tetraedron minimum var. scrobiculatum Lagerheim 1888, p. 591 

 A variety differing from the typical by having deeply punctate 

 walls. 

 Mich. 



Tedraedron muticum (A. Braun) Hansgirg 1888a, p. 131 



PI. 60, Figs. 16, 17 

 Cells small, flat, triangular, the angles without spines or furcations; 

 sides of the cell emarginate or slightly convex; cells 6-18// in 

 diameter. 



A common species in many habitats, but because of its small size 

 it is easily overlooked in rich tychoplanktonic collections. Mich., Wis. 



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