Peridinium cinctum var. tuberosum ( Meunier ) 



Lindemann 1928, p. 260 



PL 91, Figs. 7-12 



A variety larger than the typical, GSfi in diameter, 66.6/x long, 

 and more nearly globose, scarcely if at all dorsiventrally flattened; 

 in ventral view the epicone broadly rounded in general outline, 

 with angulations at the margin where it is interrupted by the sutures 

 of the plates, sometimes apiculate at the pole; plates variable, 

 usually with 4 apical, 3 intercalary, and 7 precingular plates; the 

 2 hypothecal plates produced posteriorly to form 3 stout, blunt 

 horns (the variety is described as having 3 antapical plates, but 

 Wisconsin specimens seem to have but 2 in every case); the cell 

 showing a flange that extends from the transverse furrow around 

 to the poles; plates coarsely reticulate. 



Tychoplankter; in ponds and swamps. Wis. 



Peridinium gatunense Nygaard in Ostenfeld 

 & Nygaard 1925, p. 10 (reprint) 

 PI. 90, Figs. 25, 26 

 Cells globose to elliptic, with angulations at the marginal sutures; 

 (as seen ventrally), the poles broadly rounded; transverse furrow 

 spiral with a wide border, unequally dividing the cell into a greater 

 epicone and a shorter hypocone; the longitudinal furrow extending 

 from high in the epicone to near the posterior pole; plates with 

 wide, striated sutures between them, coarsely reticulate; epitheca 

 with 13 plates; hypotheca with 2 large antapicals and 5 postcingular 

 plates; cells 55-80/x in diameter, 45-80/^ long. 

 Tychoplanktonic and euplanktonic. Wis. 



Peridinium inconspicuum Lemmermann 1900, p. 350 

 PI. 90, Figs. 22-24 



Cells small, ovoid, with the apical region shghtly produced and 

 pointed, the posterior pole broadly rounded with 2 or 3 short, sharp, 

 horn-like projections; in polar view slightly flattened dorsiventrally; 

 transverse furrow broad, without a marginal ridge, or with a very 

 narrow one (although the furrow is very deep), not spiral, dividing 

 the cell into a tall epicone and a short hypocone; longitudinal furrow 

 very broad in the hypocone, extending from the posterior pole into 

 the epicone a short distance; epitheca with 13 plates and a true apex; 

 hypotheca with 2 large antapical and 6 postcingular plates; cells 

 18.5-20/x in diameter, 22-25/^ long. 



The plants are small and the plate characteristics are seen with 

 difficulty unless empty cells are found. This species often appears in 



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