Phacus pleuronectes ( Muell. ) Dujardin 1841, p. 336 



PL 88, Fig. 16 



Cells broadly ovoid to suborbicular in outline, slightly spiral and 

 produced posteriorly to form a stout, sharp-pointed caudus which 

 is obliquely turned to the right (when seen from the ventral side); 

 anterior end broadly rounded; periplast longitudinally striated; 

 flagellum as long as or longer than the body; paramylon bodies 

 1-2 ring-like discs; cells ( 30) -37-46.8- ( 50 )/x in diameter, (42)- 

 50-80-( 100 );u long. 



This is a common species in marginal waters of eutrophic lakes, 

 especially where protected from wave action; also frequent in ponds 

 and ditches. Mich., Wis. 



Phacus pseudoswirenkoi Prescott 1944, p. 368 

 PI. 85, Fig. 26; PI. 87, Fig. 2; PI. 88, Fig. 14 



Cells orbicular in outline, abruptly narrowed posteriorly and 

 produced to form a short, sharp caudus which curves to the left 

 (when seen from the ventral side); anterior end broadly rounded; 

 flagellum about as long as the body; periplast longitudinally striated, 

 with a deep, sharp, lateral notch medianly located on the right 

 side (rarely one on the left side also); paramylon body a large, 

 circular plate; cells 30-33;u, in diameter, 37-40//, long. 



This species should be compared with P. Swirenkoi, a species 

 which is about the same size but which has entire margins and a 

 caudus which turns to the right. 



Plankter; from a cedar swamp; in ponds and ditches. Wis. 



Phacus pijrum (Ehrenb.) Stein 1878, III, Taf. 19, Figs. 51-54 



PI. 88, Fig. 22 

 Cells ovoid, narrowed gradually posteriorly to a long, straight, 

 finely pointed caudus; broadly rounded anteriorly, but with 2 pa- 

 pillae between which the flagellum emerges; periplast spirally 

 ribbed; paramylon bodies 2 ring-like plates, laterally situated; cells 

 {7)-l5.&-2lix in diameter, 27-30/x long. 

 Euplanktonic and tychoplanktonic. Mich., Wis. 



Phacus Segretii Allorge & Lefevre 1925, pp. 128, 129 



Cells broadly ovoid or unsymmetrically orbicular in outline, with- 

 out a caudus; slightly narrowed anteriorly, with a prominent ventral 

 furrow; broadly rounded posteriorly; periplast longitudinally or 

 slightly spirally striated; paramylon bodies in the form of 1 large 

 and 1 smaller circular plate; cells 20-22|U, in diameter, 22-28/i long. 



Typical form not observed in our collections. 



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