Tetraedron regulare Kuetzing 1845, p. 129 



PI. 60, Figs. 24-26 



Cells tetragonal, pyramidal, the angles produced to form stout 



lobes, narrowly rounded and tipped with a single, stout spine; the 



margins of the lobes convex or straight, lateral walls between the 



lobes concave; cells (14) -45-51. 8/x in diameter. 



Plankter; in many lakes and ponds; generally distributed. Mich., 

 Wis. 



Tetraedron regulare var. bifurcatum Wille 1884, p. 12 



PI. 61, Fig. 1 

 Cells teti'agonal, pyramidal, the sides convex or slightly concave, 

 the angles broadly rounded and tipped with 2 stout often curved 

 spines; cells 30-36/i, in diameter including spines. 



Tychoplankter; in shallow water of lakes and sloughs. Mich., Wis. 



Tetraedron regulare var. granulata Prescott 1944, p. 359 



PI. 61, Figs. 2, 3 

 Cells large, pyramidal, the lobes broad and stout with convex 



margins, the angles broadly rounded and tipped with a single short 

 spine which may be reduced to a mere papilla; wall punctate and 

 covered with small granules or roughenings; cells 35-51. 8/a in 

 diameter. 



Plankter; in several lakes. Wis. 



Tetraedron regulare var. incus Teiling 1912, pp. 274, 277 



PI. 61, Figs. 4-7 

 Cells tetragonal, flat or pyramidal, with concave lateral margins, 

 the angles slightly produced to form short lobes each tipped by a 

 relatively long spine; cells 15-20/a in diameter without spines, up to 

 37/t in diameter including spines. 

 Plankter; in several lakes. Wis. 



Tetraedron regulare var. incus fa. major Prescott 1944, p. 359 



P1.61, Fig. 13 

 Cells tetragonal, pyramidal, the margins straight or slightly convex, 

 the angles produced to form long, stout spines; cells 35-50ya in 

 diameter, including spines; spines 12-13.5/x long. 

 Plankter; lakes and streams. Wis. 



Tetraedron regulare var. torsum (Turner) Brunnthaler 1915, p. 150 



PI. 61, Figs. 8-10 

 Cells tetragonal, pyramidal, the lobes narrow and tapering to a 

 spine-tipped apex, twisted so that they are cruciately arranged; 



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