7. Cells without spines O. parvulum 



7. Cells with a spine at 1 pole 8 



8. Spine tipped with a globular thickening O. majus 



8. Spine not tipped with a thickening 9 



9. Cells strongly curved or coiled - O. cochleare 



9. Cells nearly straight, or only slightly curved, sometimes twisted, 



and often hooked at one end ( not regularly coiled ) O. elongatum 



Ophiocijtium arhuscula (A. Braun) Rabenhorst 1868, p. 68 



PI. 94, Fig. 12 

 Cells attached by a short, stout stipe, cylindrical, united in 

 corymbose families, several cells with truncate or rounded apices 

 growing from the end of a straight or slightly twisted basal cell; 

 cells 3.5— 5/A in diameter. 



Tychoplankter; in swamps. Mich., Wis. 



Ophiocytium bicuspidatum (Borge) Lemmermann 1899, p. 31 



PL 94, Fig. 23 

 Cells free-floating, arcuate or spirally twisted; poles each bearing 

 a stout spine; cells 15-20;u, in diameter, 50-55/a long without spines; 

 spines up to 40/* long. 



Plankter; in soft water lakes; generally distributed. Mich., Wis. 



Ophiocytium capitatum Wolle 1887, p. 176 

 PI. 94, Figs. 21, 22 



Cells free-floating, cylindrical, strongly curved or sickle-shaped, 

 with a short sharp spine at each pole; cells (2.7)— 5— lOju, in diam- 

 eter, 45-150- (2000)/. long. 



Common in a variety of lakes. Mich., Wis. 



Ophiocytium capitatum var. longispinum ( Moebius ) 

 Lemmermann 1899, p. 32 

 PI. 94, Fig>19 

 Cells free-floating, either straight, arcuate, or spiral, each pole 

 bearing a spine (in which character this variety differs from the 

 typical); cells 4.5-6/x in diameter; spines 16-50/i, long. 

 Tychoplankter, Wis. 



Ophiocytium, cochleare ( Eichw. ) A. Braun 1855, p. 54 

 PI. 94, Figs. 10, 11, 15 

 Cells free-floating, cylindrical, strongly arched and spirally twisted, 

 one end truncate, the other with a stout, sharp spine; cells 5-9.5/i. 

 in diameter. 



Common in the tychoplankton of many lakes and swamps. Mich., 

 Wis. 



f 363 1 



