36 



WISCONSIN PHYTOPLANKTON 



Zygospores unknown. 



Cells 40 /Lt long; maximal breadth 42.5 /*; breadth at apex 17 ft; 

 breadth at isthmus 12 /x. 



Okauchee (rr). 



14. CosMARiUM QuiNARiuM Luudell. PL 57, Fig. 28. 



Nova Acta Eeg. Soc. Upsaliae 3 Ser., 8: 28, pi. 2, fig. 14. 1871; W. & G. S. West, 

 Monogr. Brit Desm. 3: 216, pi. 85, figs. 9-10. 1908. 



Cells fairly small, length slightly greater than the breadth, deeply 

 constricted, sinus linear, with apex slightly inflated and outer margin 

 open, isthmus narrow; semicells truncate-pyramidate, with basal 

 angles broadly rounded and apical angles not acute, lateral margins 

 slightly convex and truncate apex flat ; outline of semicells granulate. 

 Vertical view elliptic. Lateral view of semicells circular. Cell wall 

 with five conspicuous granules in two rows at center of semicell, the 

 upper row with three and the lower with two granules, with a trans- 

 verse subapical row of four similar granules ; also with several smaller 

 granules near the lateral margins and two or three small granules 

 between the large ones at the center of the cell face. Chloroplast axial 

 and with two pyrenoids. (Tychoplanktont.) 



Zygospores unknown. 



Cells 42 fjL long ; 36 fx broad ; 10 [x broad at isthmus. 



Tank (rrr). 



15. CosMARiUM PUNCTULATUM Dc Brebisson. 



Mem. de la Soc. imp. d. Sc. nat. de Cherbourg 4: 129, pi. 1, fig. 16. 1856; 

 W. & G. S. West, Monogr. Brit. Desm. 3: 206, pi. 84, figs. 13-14. 1908; ibid. 4: 

 pi. 102, fig. 22. 1912. 



Cells small, length slightly greater than the breadth, deeply con- 

 stricted, sinus linear, with apex slightly inflated and outer extremity 

 open, isthmus narrow; semicells broadly subtrapeziform, with basal 

 and apical angles broadly rounded, lateral margins convex and apex 

 straight to slightly convex ; outline of semicells very finely granular. 

 Vertical view elliptic. Lateral view of semicells circular. Cell wall 

 minutely granulate near the margins and central area, if granulate, 

 with granules approximately the same size as those of the margins. 

 Chloroplasts axial, with one pyrenoid. 



Zygospores spherical, with numerous long spines with conical bases 

 and deeply emarginate to bifurcate apices, if bifurcate with the bifur- 

 cations emarginate (W. & G. S. West). 



Cells 34-36.5/1 long; 31-34 /tt broad; 8.5-11 ix broad at isthmus; 

 17-18.5 /x thick (W. & G. S. West). 



Zygospores 42-45 [i in diameter without spines, 65-68 fi with spines 

 (W. & G. S. West). 



Not found in the plankton of Wisconsin lakes. 



